diff --git a/packages/backend/src/server/api/mastodon/endpoints/account.ts b/packages/backend/src/server/api/mastodon/endpoints/account.ts
index d25f43193a..17ec9a97dd 100644
--- a/packages/backend/src/server/api/mastodon/endpoints/account.ts
+++ b/packages/backend/src/server/api/mastodon/endpoints/account.ts
@@ -154,14 +154,11 @@ export class ApiAccountMastodon {
 			reply.send(response);
 		});
 
-		fastify.get<ApiAccountMastodonRoute & { Querystring: { id?: string | string[], 'id[]'?: string | string[] }}>('/v1/accounts/relationships', async (_request, reply) => {
-			let ids = _request.query['id[]'] ?? _request.query['id'] ?? [];
-			if (typeof ids === 'string') {
-				ids = [ids];
-			}
+		fastify.get<ApiAccountMastodonRoute & { Querystring: { id?: string | string[] }}>('/v1/accounts/relationships', async (_request, reply) => {
+			if (!_request.query.id) return reply.code(400).send({ error: 'BAD_REQUEST', error_description: 'Missing required property "id"' });
 
 			const client = this.clientService.getClient(_request);
-			const data = await client.getRelationships(ids);
+			const data = await client.getRelationships(_request.query.id);
 			const response = data.data.map(relationship => convertRelationship(relationship));
 
 			reply.send(response);
diff --git a/packages/megalodon/src/megalodon.ts b/packages/megalodon/src/megalodon.ts
index 4328f41f1c..6032c351c9 100644
--- a/packages/megalodon/src/megalodon.ts
+++ b/packages/megalodon/src/megalodon.ts
@@ -342,7 +342,7 @@ export interface MegalodonInterface {
    * @param ids Array of account IDs.
    * @return Array of Relationship.
    */
-  getRelationships(ids: Array<string>): Promise<Response<Array<Entity.Relationship>>>
+  getRelationships(ids: string | Array<string>): Promise<Response<Array<Entity.Relationship>>>
   /**
    * Search for matching accounts by username or display name.
    *
diff --git a/packages/megalodon/src/misskey.ts b/packages/megalodon/src/misskey.ts
index c9a33e3130..cf6adbb70d 100644
--- a/packages/megalodon/src/misskey.ts
+++ b/packages/megalodon/src/misskey.ts
@@ -606,11 +606,16 @@ export default class Misskey implements MegalodonInterface {
    *
    * @param ids Array of account ID, for example `['1sdfag', 'ds12aa']`.
    */
-  public async getRelationships(ids: Array<string>): Promise<Response<Array<Entity.Relationship>>> {
-    return Promise.all(ids.map(id => this.getRelationship(id))).then(results => ({
-      ...results[0],
-      data: results.map(r => r.data)
-    }))
+  public async getRelationships(ids: string | Array<string>): Promise<Response<Array<Entity.Relationship>>> {
+		return this.client
+			.post<MisskeyAPI.Entity.Relation[]>('/api/users/relation', {
+				userId: ids
+			})
+			.then(res => {
+				return Object.assign(res, {
+					data: res.data.map(r => MisskeyAPI.Converter.relation(r))
+				})
+			})
   }
 
   /**