diff --git a/src/e2eTest/resources/oauth2/user.sql b/src/e2eTest/resources/oauth2/user.sql
index 351d988d..4184f284 100644
--- a/src/e2eTest/resources/oauth2/user.sql
+++ b/src/e2eTest/resources/oauth2/user.sql
@@ -44,7 +44,7 @@ Ja15+ZWbOA4vJA9pOh3x4XM=
 -----END PRIVATE KEY-----
 ', 1701398248417,
         'http://localhost/users/test-user#pubkey', 'http://localhost/users/test-user/following',
-        'http://localhost/users/test-users/followers', null, false, 0, 0, 0, null);
+        'http://localhost/users/test-users/followers', 0, false, 0, 0, 0, null);
 
 insert into user_details (actor_id, password, auto_accept_followee_follow_request)
 values ( 1730415786666758144
diff --git a/src/intTest/resources/sql/accounts/apiV1AccountsIdFollowPost フォローできる.sql b/src/intTest/resources/sql/accounts/apiV1AccountsIdFollowPost フォローできる.sql
index 2221dfc7..a2b01c22 100644
--- a/src/intTest/resources/sql/accounts/apiV1AccountsIdFollowPost フォローできる.sql	
+++ b/src/intTest/resources/sql/accounts/apiV1AccountsIdFollowPost フォローできる.sql	
@@ -7,11 +7,11 @@ VALUES (3733363, 'follow-test-user-1', 'example.com', 'follow-test-user-1-name',
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/follow-test-user-1#pubkey', 'https://example.com/users/follow-test-user-1/following',
-        'https://example.com/users/follow-test-user-1/followers', null, false, 0, 0, 0, null),
+        'https://example.com/users/follow-test-user-1/followers', 0, false, 0, 0, 0, null),
        (37335363, 'follow-test-user-2', 'example.com', 'follow-test-user-2-name', '',
         'https://example.com/users/follow-test-user-2/inbox',
         'https://example.com/users/follow-test-user-2/outbox', 'https://example.com/users/follow-test-user-2',
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/follow-test-user-2#pubkey', 'https://example.com/users/follow-test-user-2/following',
-        'https://example.com/users/follow-test-user-2/followers', null, false, 0, 0, 0, null);
+        'https://example.com/users/follow-test-user-2/followers', 0, false, 0, 0, 0, null);
diff --git a/src/intTest/resources/sql/note/httpSignature認証でフォロワーがfollowers投稿を取得できる.sql b/src/intTest/resources/sql/note/httpSignature認証でフォロワーがfollowers投稿を取得できる.sql
index f522d4bc..dc2ab9f1 100644
--- a/src/intTest/resources/sql/note/httpSignature認証でフォロワーがfollowers投稿を取得できる.sql
+++ b/src/intTest/resources/sql/note/httpSignature認証でフォロワーがfollowers投稿を取得できる.sql
@@ -7,7 +7,7 @@ VALUES (8, 'test-user8', 'example.com', 'Im test-user8.', 'THis account is test-
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user8#pubkey', 'https://example.com/users/test-user8/following',
-        'https://example.com/users/test-user8/followers', null, false, 0, 0, 0, null),
+        'https://example.com/users/test-user8/followers', 0, false, 0, 0, 0, null),
        (9, 'test-user9', 'follower.example.com', 'Im test-user9.', 'THis account is test-user9.',
         'https://follower.example.com/users/test-user9/inbox',
         'https://follower.example.com/users/test-user9/outbox', 'https://follower.example.com/users/test-user9',
@@ -15,7 +15,7 @@ VALUES (8, 'test-user8', 'example.com', 'Im test-user8.', 'THis account is test-
         null, 12345678,
         'https://follower.example.com/users/test-user9#pubkey',
         'https://follower.example.com/users/test-user9/following',
-        'https://follower.example.com/users/test-user9/followers', null, false, 0, 0, 0, null);
+        'https://follower.example.com/users/test-user9/followers', 0, false, 0, 0, 0, null);
 
 insert into relationships (actor_id, target_actor_id, following, blocking, muting, follow_request,
                            ignore_follow_request)
diff --git a/src/intTest/resources/sql/note/httpSignature認証でフォロワーがpublic投稿を取得できる.sql b/src/intTest/resources/sql/note/httpSignature認証でフォロワーがpublic投稿を取得できる.sql
index b0f688f2..a44861f4 100644
--- a/src/intTest/resources/sql/note/httpSignature認証でフォロワーがpublic投稿を取得できる.sql
+++ b/src/intTest/resources/sql/note/httpSignature認証でフォロワーがpublic投稿を取得できる.sql
@@ -7,7 +7,7 @@ VALUES (4, 'test-user4', 'example.com', 'Im test user4.', 'THis account is test
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user4#pubkey', 'https://example.com/users/test-user4/following',
-        'https://example.com/users/test-user4/followers', null, false, 0, 0, 0, null),
+        'https://example.com/users/test-user4/followers', 0, false, 0, 0, 0, null),
        (5, 'test-user5', 'follower.example.com', 'Im test user5.', 'THis account is test user5.',
         'https://follower.example.com/users/test-user5/inbox',
         'https://follower.example.com/users/test-user5/outbox', 'https://follower.example.com/users/test-user5',
@@ -15,7 +15,7 @@ VALUES (4, 'test-user4', 'example.com', 'Im test user4.', 'THis account is test
         null, 12345678,
         'https://follower.example.com/users/test-user5#pubkey',
         'https://follower.example.com/users/test-user5/following',
-        'https://follower.example.com/users/test-user5/followers', null, false, 0, 0, 0, null);
+        'https://follower.example.com/users/test-user5/followers', 0, false, 0, 0, 0, null);
 
 insert into relationships (actor_id, target_actor_id, following, blocking, muting, follow_request,
                            ignore_follow_request)
diff --git a/src/intTest/resources/sql/note/httpSignature認証でフォロワーがunlisted投稿を取得できる.sql b/src/intTest/resources/sql/note/httpSignature認証でフォロワーがunlisted投稿を取得できる.sql
index 4a271f1f..77cb3395 100644
--- a/src/intTest/resources/sql/note/httpSignature認証でフォロワーがunlisted投稿を取得できる.sql
+++ b/src/intTest/resources/sql/note/httpSignature認証でフォロワーがunlisted投稿を取得できる.sql
@@ -7,7 +7,7 @@ VALUES (6, 'test-user6', 'example.com', 'Im test-user6.', 'THis account is test-
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user6#pubkey', 'https://example.com/users/test-user6/following',
-        'https://example.com/users/test-user6/followers', null, false, 0, 0, 0, null),
+        'https://example.com/users/test-user6/followers', 0, false, 0, 0, 0, null),
        (7, 'test-user7', 'follower.example.com', 'Im test-user7.', 'THis account is test-user7.',
         'https://follower.example.com/users/test-user7/inbox',
         'https://follower.example.com/users/test-user7/outbox', 'https://follower.example.com/users/test-user7',
@@ -15,7 +15,7 @@ VALUES (6, 'test-user6', 'example.com', 'Im test-user6.', 'THis account is test-
         null, 12345678,
         'https://follower.example.com/users/test-user7#pubkey',
         'https://follower.example.com/users/test-user7/following',
-        'https://follower.example.com/users/test-user7/followers', null, false, 0, 0, 0, null);
+        'https://follower.example.com/users/test-user7/followers', 0, false, 0, 0, 0, null);
 
 insert into relationships (actor_id, target_actor_id, following, blocking, muting, follow_request,
                            ignore_follow_request)
diff --git a/src/intTest/resources/sql/note/メディア付き投稿はattachmentにDocumentとして画像が存在する.sql b/src/intTest/resources/sql/note/メディア付き投稿はattachmentにDocumentとして画像が存在する.sql
index b99b289f..6cc9db8c 100644
--- a/src/intTest/resources/sql/note/メディア付き投稿はattachmentにDocumentとして画像が存在する.sql
+++ b/src/intTest/resources/sql/note/メディア付き投稿はattachmentにDocumentとして画像が存在する.sql
@@ -7,7 +7,7 @@ VALUES (11, 'test-user11', 'example.com', 'Im test-user11.', 'THis account is te
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user11#pubkey', 'https://example.com/users/test-user11/following',
-        'https://example.com/users/test-user11/followers', null, false, 0, 0, 0, null);
+        'https://example.com/users/test-user11/followers', 0, false, 0, 0, 0, null);
 
 insert into POSTS (id, actor_id, overview, content, text, created_at, visibility, url, repost_id, reply_id, sensitive,
                    ap_id,
diff --git a/src/intTest/resources/sql/note/リプライになっている投稿はinReplyToが存在する.sql b/src/intTest/resources/sql/note/リプライになっている投稿はinReplyToが存在する.sql
index 67178345..41ac73a4 100644
--- a/src/intTest/resources/sql/note/リプライになっている投稿はinReplyToが存在する.sql
+++ b/src/intTest/resources/sql/note/リプライになっている投稿はinReplyToが存在する.sql
@@ -7,7 +7,7 @@ VALUES (10, 'test-user10', 'example.com', 'Im test-user10.', 'THis account is te
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user10#pubkey', 'https://example.com/users/test-user10/following',
-        'https://example.com/users/test-user10/followers', null, false, 0, 0, 0, null);
+        'https://example.com/users/test-user10/followers', 0, false, 0, 0, 0, null);
 
 insert into POSTS (id, actor_id, overview, content, text, created_at, visibility, url, repost_id, reply_id, sensitive,
                    ap_id,
diff --git a/src/intTest/resources/sql/note/匿名でfollowers投稿を取得しようとすると404.sql b/src/intTest/resources/sql/note/匿名でfollowers投稿を取得しようとすると404.sql
index b848530c..250cfb5a 100644
--- a/src/intTest/resources/sql/note/匿名でfollowers投稿を取得しようとすると404.sql
+++ b/src/intTest/resources/sql/note/匿名でfollowers投稿を取得しようとすると404.sql
@@ -7,7 +7,7 @@ VALUES (3, 'test-user3', 'example.com', 'Im test user3.', 'THis account is test
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user3#pubkey', 'https://example.com/users/test-user3/following',
-        'https://example.com/users/test-user3/followers', null, false, 0, 0, 0, null);
+        'https://example.com/users/test-user3/followers', 0, false, 0, 0, 0, null);
 
 insert into POSTS (id, actor_id, overview, content, text, created_at, visibility, url, repost_id, reply_id, sensitive,
                    ap_id,
diff --git a/src/intTest/resources/sql/note/匿名でpublic投稿を取得できる.sql b/src/intTest/resources/sql/note/匿名でpublic投稿を取得できる.sql
index 0a3272b8..777f9244 100644
--- a/src/intTest/resources/sql/note/匿名でpublic投稿を取得できる.sql
+++ b/src/intTest/resources/sql/note/匿名でpublic投稿を取得できる.sql
@@ -7,7 +7,7 @@ VALUES (1, 'test-user', 'example.com', 'Im test user.', 'THis account is test us
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user#pubkey', 'https://example.com/users/test-user/following',
-        'https://example.com/users/test-users/followers', null, false, 0, 0, 0, null);
+        'https://example.com/users/test-users/followers', 0, false, 0, 0, 0, null);
 
 insert into POSTS (id, actor_id, overview, content, text, created_at, visibility, url, repost_id, reply_id, sensitive,
                    ap_id,
diff --git a/src/intTest/resources/sql/note/匿名でunlisted投稿を取得できる.sql b/src/intTest/resources/sql/note/匿名でunlisted投稿を取得できる.sql
index abeb3150..b132734d 100644
--- a/src/intTest/resources/sql/note/匿名でunlisted投稿を取得できる.sql
+++ b/src/intTest/resources/sql/note/匿名でunlisted投稿を取得できる.sql
@@ -7,7 +7,7 @@ VALUES (2, 'test-user2', 'example.com', 'Im test user2.', 'THis account is test
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user2#pubkey', 'https://example.com/users/test-user2/following',
-        'https://example.com/users/test-user2/followers', null, false, 0, 0, 0, null);
+        'https://example.com/users/test-user2/followers', 0, false, 0, 0, 0, null);
 
 insert into POSTS (id, actor_id, overview, content, text, created_at, visibility, url, repost_id, reply_id, sensitive,
                    ap_id,
diff --git a/src/intTest/resources/sql/test-user.sql b/src/intTest/resources/sql/test-user.sql
index cdcc686d..d46e5280 100644
--- a/src/intTest/resources/sql/test-user.sql
+++ b/src/intTest/resources/sql/test-user.sql
@@ -7,4 +7,4 @@ VALUES (1, 'test-user', 'example.com', 'Im test user.', 'THis account is test us
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user#pubkey', 'https://example.com/users/test-user/following',
-        'https://example.com/users/test-users/followers', null, false, 0, 0, 0, null);
+        'https://example.com/users/test-users/followers', 0, false, 0, 0, 0, null);
diff --git a/src/intTest/resources/sql/test-user2.sql b/src/intTest/resources/sql/test-user2.sql
index ef455c75..0f736704 100644
--- a/src/intTest/resources/sql/test-user2.sql
+++ b/src/intTest/resources/sql/test-user2.sql
@@ -7,4 +7,4 @@ VALUES (2, 'test-user2', 'example.com', 'Im test user.', 'THis account is test u
         '-----BEGIN PUBLIC KEY-----...-----END PUBLIC KEY-----',
         '-----BEGIN PRIVATE KEY-----...-----END PRIVATE KEY-----', 12345678,
         'https://example.com/users/test-user2#pubkey', 'https://example.com/users/test-user2/following',
-        'https://example.com/users/test-user2s/followers', null, false, 0, 0, 0, null);
+        'https://example.com/users/test-user2s/followers', 0, false, 0, 0, 0, null);
diff --git a/src/main/kotlin/dev/usbharu/hideout/core/domain/model/actor/Actor.kt b/src/main/kotlin/dev/usbharu/hideout/core/domain/model/actor/Actor.kt
index 1bfb4905..eee1e824 100644
--- a/src/main/kotlin/dev/usbharu/hideout/core/domain/model/actor/Actor.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/core/domain/model/actor/Actor.kt
@@ -51,8 +51,8 @@ data class Actor private constructor(
     val keyId: String,
     val followers: String? = null,
     val following: String? = null,
-    @get:Positive
-    val instance: Long? = null,
+    @get:PositiveOrZero
+    val instance: Long,
     val locked: Boolean,
     val followersCount: Int = 0,
     val followingCount: Int = 0,
@@ -86,7 +86,7 @@ data class Actor private constructor(
             keyId: String,
             following: String? = null,
             followers: String? = null,
-            instance: Long? = null,
+            instance: Long,
             locked: Boolean,
             followersCount: Int = 0,
             followingCount: Int = 0,
diff --git a/src/main/kotlin/dev/usbharu/hideout/core/infrastructure/exposedrepository/ActorRepositoryImpl.kt b/src/main/kotlin/dev/usbharu/hideout/core/infrastructure/exposedrepository/ActorRepositoryImpl.kt
index 67c33051..08bc5de4 100644
--- a/src/main/kotlin/dev/usbharu/hideout/core/infrastructure/exposedrepository/ActorRepositoryImpl.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/core/infrastructure/exposedrepository/ActorRepositoryImpl.kt
@@ -167,7 +167,7 @@ object Actors : Table("actors") {
     val keyId = varchar("key_id", length = 1000)
     val following = varchar("following", length = 1000).nullable()
     val followers = varchar("followers", length = 1000).nullable()
-    val instance = long("instance").references(Instance.id).nullable()
+    val instance = long("instance").references(Instance.id)
     val locked = bool("locked")
     val followingCount = integer("following_count")
     val followersCount = integer("followers_count")
diff --git a/src/main/kotlin/dev/usbharu/hideout/core/service/user/UserServiceImpl.kt b/src/main/kotlin/dev/usbharu/hideout/core/service/user/UserServiceImpl.kt
index 5a459405..294656ca 100644
--- a/src/main/kotlin/dev/usbharu/hideout/core/service/user/UserServiceImpl.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/core/service/user/UserServiceImpl.kt
@@ -78,7 +78,8 @@ class UserServiceImpl(
             following = "$userUrl/following",
             followers = "$userUrl/followers",
             keyId = "$userUrl#pubkey",
-            locked = false
+            locked = false,
+            instance = 0
         )
         val save = actorRepository.save(userEntity)
         userDetailRepository.save(UserDetail(nextId, hashedPassword, true))
@@ -95,13 +96,7 @@ class UserServiceImpl(
             throw IllegalStateException("Cannot create Deleted actor.")
         }
 
-        @Suppress("TooGenericExceptionCaught")
-        val instance = try {
-            instanceService.fetchInstance(user.url, user.sharedInbox)
-        } catch (e: Exception) {
-            logger.warn("FAILED to fetch instance. url: {}", user.url, e)
-            null
-        }
+        val instance = instanceService.fetchInstance(user.url, user.sharedInbox)
 
         val nextId = actorRepository.nextId()
         val userEntity = actorBuilder.of(
@@ -118,7 +113,7 @@ class UserServiceImpl(
             followers = user.followers,
             following = user.following,
             keyId = user.keyId,
-            instance = instance?.id,
+            instance = instance.id,
             locked = user.locked ?: false
         )
         return try {
diff --git a/src/main/resources/db/migration/V1__Init_DB.sql b/src/main/resources/db/migration/V1__Init_DB.sql
index 4b76304f..09f4f0ca 100644
--- a/src/main/resources/db/migration/V1__Init_DB.sql
+++ b/src/main/resources/db/migration/V1__Init_DB.sql
@@ -45,7 +45,7 @@ create table if not exists actors
     key_id          varchar(1000)  not null,
     "following"     varchar(1000)  null,
     followers       varchar(1000)  null,
-    "instance"      bigint         null,
+    "instance" bigint not null,
     locked          boolean        not null,
     following_count int            not null,
     followers_count int            not null,
@@ -240,10 +240,14 @@ create table if not exists relationships
     unique (actor_id, target_actor_id)
 );
 
+insert into instance (id, name, description, url, icon_url, shared_inbox, software, version, is_blocked, is_muted,
+                      moderation_note, created_at)
+values (0, 'system', '', '', '', null, '', '', false, false, '', current_timestamp);
+
 insert into actors (id, name, domain, screen_name, description, inbox, outbox, url, public_key, private_key, created_at,
                     key_id, following, followers, instance, locked, following_count, followers_count, posts_count,
                     last_post_at)
-values (0, 'ghost', '', '', '', '', '', '', '', null, 0, '', '', '', null, true, 0, 0, 0, null);
+values (0, 'ghost', '', '', '', '', '', '', '', null, 0, '', '', '', 0, true, 0, 0, 0, null);
 
 create table if not exists deleted_actors
 (
diff --git a/src/test/kotlin/dev/usbharu/hideout/core/service/user/ActorServiceTest.kt b/src/test/kotlin/dev/usbharu/hideout/core/service/user/ActorServiceTest.kt
index c44479cc..846c0d9e 100644
--- a/src/test/kotlin/dev/usbharu/hideout/core/service/user/ActorServiceTest.kt
+++ b/src/test/kotlin/dev/usbharu/hideout/core/service/user/ActorServiceTest.kt
@@ -22,6 +22,8 @@ import dev.usbharu.hideout.application.config.ApplicationConfig
 import dev.usbharu.hideout.application.config.CharacterLimit
 import dev.usbharu.hideout.core.domain.model.actor.Actor
 import dev.usbharu.hideout.core.domain.model.actor.ActorRepository
+import dev.usbharu.hideout.core.domain.model.instance.Instance
+import dev.usbharu.hideout.core.service.instance.InstanceService
 import jakarta.validation.Validation
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.test.runTest
@@ -31,6 +33,7 @@ import org.mockito.kotlin.*
 import utils.TestApplicationConfig.testApplicationConfig
 import java.net.URL
 import java.security.KeyPairGenerator
+import java.time.Instant
 import kotlin.test.assertEquals
 import kotlin.test.assertNull
 
@@ -40,6 +43,7 @@ class ActorServiceTest {
         ApplicationConfig(URL("https://example.com")),
         Validation.buildDefaultValidatorFactory().validator
     )
+
     @Test
     fun `createLocalUser ローカルユーザーを作成できる`() = runTest {
 
@@ -90,13 +94,34 @@ class ActorServiceTest {
             onBlocking { nextId() } doReturn 113345L
         }
 
+        val instanceService = mock<InstanceService> {
+            onBlocking {
+                fetchInstance(
+                    eq("https://remote.example.com"),
+                    isNull()
+                )
+            } doReturn Instance(
+                12345L,
+                "",
+                "",
+                "https://remote.example.com",
+                "https://remote.example.com/favicon.ico",
+                null,
+                "unknown",
+                "",
+                false,
+                false,
+                "",
+                Instant.now()
+            )
+        }
         val userService =
             UserServiceImpl(
                 actorRepository = actorRepository,
                 userAuthService = mock(),
                 actorBuilder = actorBuilder,
                 applicationConfig = testApplicationConfig,
-                instanceService = mock(),
+                instanceService = instanceService,
                 userDetailRepository = mock(),
                 deletedActorRepository = mock(),
                 reactionRepository = mock(),
diff --git a/src/test/kotlin/utils/UserBuilder.kt b/src/test/kotlin/utils/UserBuilder.kt
index 4f28ea93..0aff8e44 100644
--- a/src/test/kotlin/utils/UserBuilder.kt
+++ b/src/test/kotlin/utils/UserBuilder.kt
@@ -64,7 +64,8 @@ object UserBuilder {
             keyId = keyId,
             followers = followers,
             following = following,
-            locked = false
+            locked = false,
+            instance = 0
         )
     }
 
@@ -82,6 +83,7 @@ object UserBuilder {
         keyId: String = "https://$domain/$id#pubkey",
         followers: String = "https://$domain/$id/followers",
         following: String = "https://$domain/$id/following",
+        instanceId: Long = generateId(),
     ): Actor {
         return actorBuilder.of(
             id = id,
@@ -98,7 +100,8 @@ object UserBuilder {
             keyId = keyId,
             followers = followers,
             following = following,
-            locked = false
+            locked = false,
+            instance = instanceId
         )
     }