diff --git a/server/router/api/v1/memo_service_converter.go b/server/router/api/v1/memo_service_converter.go
index c8433c3a2..139cbfaba 100644
--- a/server/router/api/v1/memo_service_converter.go
+++ b/server/router/api/v1/memo_service_converter.go
@@ -43,15 +43,9 @@ func (s *APIV1Service) convertMemoFromStore(ctx context.Context, memo *store.Mem
 		memoMessage.Property = convertMemoPropertyFromStore(memo.Payload.Property)
 		memoMessage.Location = convertLocationFromStore(memo.Payload.Location)
 	}
-	if memo.ParentID != nil {
-		parent, err := s.Store.GetMemo(ctx, &store.FindMemo{
-			ID:             memo.ParentID,
-			ExcludeContent: true,
-		})
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to get parent memo")
-		}
-		parentName := fmt.Sprintf("%s%s", MemoNamePrefix, parent.UID)
+
+	if memo.ParentUID != nil {
+		parentName := fmt.Sprintf("%s%s", MemoNamePrefix, *memo.ParentUID)
 		memoMessage.Parent = &parentName
 	}
 
diff --git a/store/db/mysql/memo.go b/store/db/mysql/memo.go
index 7d59e431b..354aab545 100644
--- a/store/db/mysql/memo.go
+++ b/store/db/mysql/memo.go
@@ -90,7 +90,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 		where = append(where, fmt.Sprintf("`memo`.`visibility` in (%s)", strings.Join(placeholder, ",")))
 	}
 	if find.ExcludeComments {
-		having = append(having, "`parent_id` IS NULL")
+		having = append(having, "`parent_uid` IS NULL")
 	}
 
 	order := "DESC"
@@ -113,7 +113,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 		"`memo`.`visibility` AS `visibility`",
 		"`memo`.`pinned` AS `pinned`",
 		"`memo`.`payload` AS `payload`",
-		"`memo_relation`.`related_memo_id` AS `parent_id`",
+		"CASE WHEN `parent_memo`.`uid` IS NOT NULL THEN `parent_memo`.`uid` ELSE NULL END AS `parent_uid`",
 	}
 	if !find.ExcludeContent {
 		fields = append(fields, "`memo`.`content` AS `content`")
@@ -121,6 +121,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 
 	query := "SELECT " + strings.Join(fields, ", ") + " FROM `memo`" + " " +
 		"LEFT JOIN `memo_relation` ON `memo`.`id` = `memo_relation`.`memo_id` AND `memo_relation`.`type` = 'COMMENT'" + " " +
+		"LEFT JOIN `memo` AS `parent_memo` ON `memo_relation`.`related_memo_id` = `parent_memo`.`id`" + " " +
 		"WHERE " + strings.Join(where, " AND ") + " " +
 		"HAVING " + strings.Join(having, " AND ") + " " +
 		"ORDER BY " + strings.Join(orderBy, ", ")
@@ -151,7 +152,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 			&memo.Visibility,
 			&memo.Pinned,
 			&payloadBytes,
-			&memo.ParentID,
+			&memo.ParentUID,
 		}
 		if !find.ExcludeContent {
 			dests = append(dests, &memo.Content)
diff --git a/store/db/postgres/memo.go b/store/db/postgres/memo.go
index b30d0bc11..0400165a7 100644
--- a/store/db/postgres/memo.go
+++ b/store/db/postgres/memo.go
@@ -105,7 +105,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 		`memo.visibility AS visibility`,
 		`memo.pinned AS pinned`,
 		`memo.payload AS payload`,
-		`memo_relation.related_memo_id AS parent_id`,
+		`CASE WHEN parent_memo.uid IS NOT NULL THEN parent_memo.uid ELSE NULL END AS parent_uid`,
 	}
 	if !find.ExcludeContent {
 		fields = append(fields, `memo.content AS content`)
@@ -114,6 +114,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 	query := `SELECT ` + strings.Join(fields, ", ") + `
 		FROM memo
 		LEFT JOIN memo_relation ON memo.id = memo_relation.memo_id AND memo_relation.type = 'COMMENT'
+		LEFT JOIN memo AS parent_memo ON memo_relation.related_memo_id = parent_memo.id
 		WHERE ` + strings.Join(where, " AND ") + `
 		ORDER BY ` + strings.Join(orderBy, ", ")
 	if find.Limit != nil {
@@ -143,7 +144,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 			&memo.Visibility,
 			&memo.Pinned,
 			&payloadBytes,
-			&memo.ParentID,
+			&memo.ParentUID,
 		}
 		if !find.ExcludeContent {
 			dests = append(dests, &memo.Content)
diff --git a/store/db/sqlite/memo.go b/store/db/sqlite/memo.go
index 73f628a7e..74e0b87b6 100644
--- a/store/db/sqlite/memo.go
+++ b/store/db/sqlite/memo.go
@@ -82,7 +82,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 		where = append(where, fmt.Sprintf("`memo`.`visibility` IN (%s)", strings.Join(placeholder, ",")))
 	}
 	if find.ExcludeComments {
-		where = append(where, "`parent_id` IS NULL")
+		where = append(where, "`parent_uid` IS NULL")
 	}
 
 	order := "DESC"
@@ -105,7 +105,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 		"`memo`.`visibility` AS `visibility`",
 		"`memo`.`pinned` AS `pinned`",
 		"`memo`.`payload` AS `payload`",
-		"`memo_relation`.`related_memo_id` AS `parent_id`",
+		"CASE WHEN `parent_memo`.`uid` IS NOT NULL THEN `parent_memo`.`uid` ELSE NULL END AS `parent_uid`",
 	}
 	if !find.ExcludeContent {
 		fields = append(fields, "`memo`.`content` AS `content`")
@@ -113,6 +113,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 
 	query := "SELECT " + strings.Join(fields, ", ") + "FROM `memo` " +
 		"LEFT JOIN `memo_relation` ON `memo`.`id` = `memo_relation`.`memo_id` AND `memo_relation`.`type` = \"COMMENT\" " +
+		"LEFT JOIN `memo` AS `parent_memo` ON `memo_relation`.`related_memo_id` = `parent_memo`.`id` " +
 		"WHERE " + strings.Join(where, " AND ") + " " +
 		"ORDER BY " + strings.Join(orderBy, ", ")
 	if find.Limit != nil {
@@ -142,7 +143,7 @@ func (d *DB) ListMemos(ctx context.Context, find *store.FindMemo) ([]*store.Memo
 			&memo.Visibility,
 			&memo.Pinned,
 			&payloadBytes,
-			&memo.ParentID,
+			&memo.ParentUID,
 		}
 		if !find.ExcludeContent {
 			dests = append(dests, &memo.Content)
diff --git a/store/memo.go b/store/memo.go
index a3a10a075..bdff1f106 100644
--- a/store/memo.go
+++ b/store/memo.go
@@ -52,7 +52,7 @@ type Memo struct {
 	Payload    *storepb.MemoPayload
 
 	// Composed fields
-	ParentID *int32
+	ParentUID *string
 }
 
 type FindMemo struct {