diff --git a/AquaNet/src/libs/generalTypes.ts b/AquaNet/src/libs/generalTypes.ts
index 60b90026..5c6535d4 100644
--- a/AquaNet/src/libs/generalTypes.ts
+++ b/AquaNet/src/libs/generalTypes.ts
@@ -99,6 +99,7 @@ export interface GenericGameSummary {
   lastVersion: string
   ratingComposition: { [key: string]: any }
   recent: GenericGamePlaylog[]
+  rival?: boolean
 }
 
 export interface MusicMeta {
diff --git a/AquaNet/src/libs/i18n/en_ref.ts b/AquaNet/src/libs/i18n/en_ref.ts
index c34fbda8..aab83acc 100644
--- a/AquaNet/src/libs/i18n/en_ref.ts
+++ b/AquaNet/src/libs/i18n/en_ref.ts
@@ -24,6 +24,8 @@ export const EN_REF_USER = {
   'UserHome.RankDetail.Title': 'Achievement Details',
   'UserHome.RankDetail.Level': 'Level',
   'UserHome.B50': 'B50',
+  'UserHome.AddRival': "Add to Rival",
+  'UserHome.RemoveRival': "Remove from Rival",
 }
 
 export const EN_REF_Welcome = {
diff --git a/AquaNet/src/libs/i18n/zh.ts b/AquaNet/src/libs/i18n/zh.ts
index a33ef8fd..1085c142 100644
--- a/AquaNet/src/libs/i18n/zh.ts
+++ b/AquaNet/src/libs/i18n/zh.ts
@@ -33,6 +33,8 @@ const zhUser: typeof EN_REF_USER = {
   'UserHome.RankDetail.Title': '评分详细',
   'UserHome.RankDetail.Level': "等级",
   'UserHome.B50': "B50",
+  'UserHome.AddRival': "添加劲敌",
+  'UserHome.RemoveRival': "移除劲敌",
 }
 
 const zhWelcome: typeof EN_REF_Welcome = {
diff --git a/AquaNet/src/libs/sdk.ts b/AquaNet/src/libs/sdk.ts
index 8c11293b..4b08c481 100644
--- a/AquaNet/src/libs/sdk.ts
+++ b/AquaNet/src/libs/sdk.ts
@@ -305,6 +305,8 @@ export const GAME = {
     post(`/api/v2/game/${game}/export`),
   import: (game: GameName, data: any): Promise<Record<string, any>> =>
     post(`/api/v2/game/${game}/import`, {}, { body: JSON.stringify(data) }),
+  setRival: (game: GameName, rivalUserName: string, isAdd: boolean) =>
+    post(`/api/v2/game/${game}/set-rival`, { rivalUserName, isAdd }),
 }
 
 export const DATA = {
diff --git a/AquaNet/src/pages/UserHome.svelte b/AquaNet/src/pages/UserHome.svelte
index 6bc62509..d32aed43 100644
--- a/AquaNet/src/pages/UserHome.svelte
+++ b/AquaNet/src/pages/UserHome.svelte
@@ -47,6 +47,7 @@
 
   let allMusics: AllMusic
   let showDetailRank = false
+  let isLoading = false
   USER.isLoggedIn() && USER.me().then(u => me = u)
 
 
@@ -90,6 +91,13 @@
       })
     }).catch((e) => error = e.message);
   }).catch((e) => { error = e.message; console.error(e) } );
+
+  const setRival = (isAdd: boolean) => {
+    isLoading = true
+    GAME.setRival(game, username, isAdd).then(() => {
+      d!.user.rival = isAdd
+    }).catch(e => error = e.message).finally(() => isLoading = false)
+  }
 </script>
 
 <main id="user-home" class="content">
@@ -98,6 +106,11 @@
       <img use:pfp={d.user.aquaUser} alt="" class="pfp" on:error={pfpNotFound}>
       <div class="name-box">
         <h2>{d.user.name}</h2>
+        {#if typeof d.user.rival === 'boolean' && game === 'mai2'}
+          <a class="clickable" on:click={()=>setRival(!d.user.rival)}>
+            {d.user.rival ? t("UserHome.RemoveRival") : t("UserHome.AddRival")}
+          </a>
+        {/if}
         {#if me && me.username === username}
           <a class="setting-icon clickable" use:tooltip={t("UserHome.Settings")} href="/settings">
             <Icon icon="eos-icons:rotating-gear"/>
@@ -267,7 +280,7 @@
     </div>
   {/if}
 
-  <StatusOverlays {error} loading={!d} />
+  <StatusOverlays {error} loading={!d || isLoading} />
 </main>
 
 <style lang="sass">
diff --git a/src/main/java/icu/samnyan/aqua/net/games/GameApiController.kt b/src/main/java/icu/samnyan/aqua/net/games/GameApiController.kt
index 3a6f9218..a5a42339 100644
--- a/src/main/java/icu/samnyan/aqua/net/games/GameApiController.kt
+++ b/src/main/java/icu/samnyan/aqua/net/games/GameApiController.kt
@@ -24,7 +24,7 @@ abstract class GameApiController<T : IUserData>(name: String, userDataClass: KCl
     @API("trend")
     abstract suspend fun trend(@RP username: String): List<TrendOut>
     @API("user-summary")
-    abstract suspend fun userSummary(@RP username: String): GenericGameSummary
+    abstract suspend fun userSummary(@RP username: String, @RP token: String?): GenericGameSummary
 
     @API("recent")
     suspend fun recent(@RP username: String): List<IGenericGamePlaylog> = us.cardByName(username) { card ->
@@ -93,7 +93,7 @@ abstract class GameApiController<T : IUserData>(name: String, userDataClass: KCl
         }
     }
 
-    fun genericUserSummary(card: Card, ratingComp: Map<String, String>): GenericGameSummary {
+    fun genericUserSummary(card: Card, ratingComp: Map<String, String>, rival: Boolean? = null): GenericGameSummary {
         // Summary values: total plays, player rating, server-wide ranking
         // number of each rank, max combo, number of full combo, number of all perfect
         val user = userDataRepo.findByCard(card) ?: (404 - "Game data not found")
@@ -138,7 +138,8 @@ abstract class GameApiController<T : IUserData>(name: String, userDataClass: KCl
             lastVersion = user.lastRomVersion,
             ratingComposition = ratingComp,
             recent = plays.sortedBy { it.userPlayDate.toString() }.takeLast(15).reversed(),
-            lastPlayedHost = us.userRepo.findByKeychip(user.lastClientId)?.username
+            lastPlayedHost = us.userRepo.findByKeychip(user.lastClientId)?.username,
+            rival = rival
         )
     }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/icu/samnyan/aqua/net/games/Models.kt b/src/main/java/icu/samnyan/aqua/net/games/Models.kt
index 095fb6e3..5db8f7de 100644
--- a/src/main/java/icu/samnyan/aqua/net/games/Models.kt
+++ b/src/main/java/icu/samnyan/aqua/net/games/Models.kt
@@ -45,7 +45,9 @@ data class GenericGameSummary(
 
     val ratingComposition: Map<String, Any>,
 
-    val recent: List<IGenericGamePlaylog>
+    val recent: List<IGenericGamePlaylog>,
+
+    val rival: Boolean?
 )
 
 data class GenericRankingPlayer(
diff --git a/src/main/java/icu/samnyan/aqua/net/games/chu3/Chusan.kt b/src/main/java/icu/samnyan/aqua/net/games/chu3/Chusan.kt
index e6debddb..08a9d42b 100644
--- a/src/main/java/icu/samnyan/aqua/net/games/chu3/Chusan.kt
+++ b/src/main/java/icu/samnyan/aqua/net/games/chu3/Chusan.kt
@@ -29,7 +29,7 @@ class Chusan(
         "userName" to usernameCheck(SEGA_USERNAME_CAHRS)
     ) }
 
-    override suspend fun userSummary(@RP username: Str) = us.cardByName(username) { card ->
+    override suspend fun userSummary(@RP username: Str, @RP token: String?) = us.cardByName(username) { card ->
         // Summary values: total plays, player rating, server-wide ranking
         // number of each rank, max combo, number of full combo, number of all perfect
         val extra = userGeneralDataRepository.findByUser_Card_ExtId(card.extId)
@@ -41,4 +41,4 @@ class Chusan(
 
         genericUserSummary(card, ratingComposition)
     }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/icu/samnyan/aqua/net/games/mai2/Maimai2.kt b/src/main/java/icu/samnyan/aqua/net/games/mai2/Maimai2.kt
index 643caafb..927e915f 100644
--- a/src/main/java/icu/samnyan/aqua/net/games/mai2/Maimai2.kt
+++ b/src/main/java/icu/samnyan/aqua/net/games/mai2/Maimai2.kt
@@ -17,7 +17,7 @@ class Maimai2(
     override val playlogRepo: Mai2UserPlaylogRepo,
     override val userDataRepo: Mai2UserDataRepo,
     val repos: Mai2Repos,
-): GameApiController<Mai2UserDetail>("mai2", Mai2UserDetail::class) {
+) : GameApiController<Mai2UserDetail>("mai2", Mai2UserDetail::class) {
     override suspend fun trend(@RP username: Str): List<TrendOut> = us.cardByName(username) { card ->
         findTrend(playlogRepo.findByUserCardExtId(card.extId)
             .map { TrendLog(it.playDate, it.afterRating) })
@@ -25,11 +25,13 @@ class Maimai2(
 
     // Only show > S rank
     override val shownRanks = mai2Scores.filter { it.first >= 97 * 10000 }
-    override val settableFields: Map<String, (Mai2UserDetail, String) -> Unit> by lazy { mapOf(
-        "userName" to usernameCheck(SEGA_USERNAME_CAHRS),
-    ) }
+    override val settableFields: Map<String, (Mai2UserDetail, String) -> Unit> by lazy {
+        mapOf(
+            "userName" to usernameCheck(SEGA_USERNAME_CAHRS),
+        )
+    }
 
-    override suspend fun userSummary(@RP username: Str) = us.cardByName(username) { card ->
+    override suspend fun userSummary(@RP username: Str, @RP token: String?) = us.cardByName(username) { card ->
         val extra = repos.userGeneralData.findByUser_Card_ExtId(card.extId)
             .associate { it.propertyKey to it.propertyValue }
 
@@ -38,7 +40,20 @@ class Maimai2(
             "best15" to (extra["recent_rating_new"] ?: "")
         )
 
-        genericUserSummary(card, ratingComposition)
+        // if isLogin than boolean or null
+        // use the type to check user login in frontend
+        val isMyRival = token?.let { t ->
+            us.jwt.auth(t) { u ->
+                if (u.username == username) return@auth null
+                us.cardByName(u.username) { myCard ->
+                    val user = repos.userData.findByCardExtId(card.extId).orElse(null) ?: (404 - "User not found")
+                    val myRival = repos.userGeneralData.findByUser_Card_ExtIdAndPropertyKey(myCard.extId, "favorite_rival").map { it.propertyValue.split(',') }.orElse(emptyList()).map { it.long() }
+                    myRival.contains(user.id)
+                }
+            }
+        }
+
+        genericUserSummary(card, ratingComposition, isMyRival)
     }
 
     @API("user-rating")
@@ -100,4 +115,30 @@ class Maimai2(
         }
         mapOf("newName" to newNameFull)
     }
+
+    @PostMapping("set-rival")
+    suspend fun setRival(@RP token: String, @RP rivalUserName: String, @RP isAdd: Boolean) = us.jwt.auth(token) { u ->
+        us.cardByName(u.username) { myCard ->
+            val rivalCard = us.cardByName(rivalUserName) { it }
+            val rivalUser = repos.userData.findByCardExtId(rivalCard.extId).orElse(null) ?: (404 - "User not found")
+            val myRival = repos.userGeneralData.findByUser_Card_ExtIdAndPropertyKey(myCard.extId, "favorite_rival").orElse(null)
+                ?: Mai2UserGeneralData().apply {
+                    user = repos.userData.findByCardExtId(myCard.extId).orElse(null) ?: (404 - "User not found")
+                    propertyKey = "favorite_rival"
+                }
+            val myRivalList = myRival.propertyValue.split(',').toMutableSet()
+
+            if (isAdd && myRivalList.size >= 4) {
+                (400 - "Rival list is full")
+            } else if (isAdd) {
+                myRivalList.add(rivalUser.id.toString())
+            } else {
+                myRivalList.remove(rivalUser.id.toString())
+            }
+
+            myRival.propertyValue = myRivalList.joinToString(",")
+            repos.userGeneralData.save(myRival)
+        }
+        SUCCESS
+    }
 }
diff --git a/src/main/java/icu/samnyan/aqua/net/games/ongeki/Ongeki.kt b/src/main/java/icu/samnyan/aqua/net/games/ongeki/Ongeki.kt
index d248951a..4cca0091 100644
--- a/src/main/java/icu/samnyan/aqua/net/games/ongeki/Ongeki.kt
+++ b/src/main/java/icu/samnyan/aqua/net/games/ongeki/Ongeki.kt
@@ -28,7 +28,7 @@ class Ongeki(
         "userName" to usernameCheck(SEGA_USERNAME_CAHRS)
     ) }
 
-    override suspend fun userSummary(username: String) = us.cardByName(username) { card ->
+    override suspend fun userSummary(username: String, token: String?) = us.cardByName(username) { card ->
         val extra = userGeneralDataRepository.findByUser_Card_ExtId(card.extId)
             .associate { it.propertyKey to it.propertyValue }
 
@@ -40,4 +40,4 @@ class Ongeki(
 
         genericUserSummary(card, ratingComposition)
     }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/icu/samnyan/aqua/net/games/wacca/Wacca.kt b/src/main/java/icu/samnyan/aqua/net/games/wacca/Wacca.kt
index 527457a6..ee2a5346 100644
--- a/src/main/java/icu/samnyan/aqua/net/games/wacca/Wacca.kt
+++ b/src/main/java/icu/samnyan/aqua/net/games/wacca/Wacca.kt
@@ -25,10 +25,10 @@ class Wacca(
             .map { TrendLog(it.userPlayDate.utc().isoDate(), it.afterRating) })
     }
 
-    override suspend fun userSummary(@RP username: String) = us.cardByName(username) { card ->
+    override suspend fun userSummary(@RP username: String, @RP token: String?) = us.cardByName(username) { card ->
         // TODO: Rating composition
         genericUserSummary(card, mapOf())
     }
 
     override val shownRanks: List<Pair<Int, String>> = waccaScores.filter { it.first > 85 * 10000 }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/icu/samnyan/aqua/sega/maimai2/Maimai2ServletController.kt b/src/main/java/icu/samnyan/aqua/sega/maimai2/Maimai2ServletController.kt
index f69cdc9d..0fa746c9 100644
--- a/src/main/java/icu/samnyan/aqua/sega/maimai2/Maimai2ServletController.kt
+++ b/src/main/java/icu/samnyan/aqua/sega/maimai2/Maimai2ServletController.kt
@@ -122,11 +122,13 @@ class Maimai2ServletController(
     val getUserRivalData = UserReqHandler { req, userId ->
         val rivalId = parsing { (req["rivalId"] as Number).toLong() }
 
+        // rivalId should store and fetch with the id column of table rather than card_ext_id
+        // or user will be able to get others' ext_id by setting them as rival
         mapOf(
             "userId" to userId,
             "userRivalData" to mapOf(
                 "rivalId" to rivalId,
-                "rivalName" to (repos.userData.findByCardExtId(rivalId)()?.userName ?: "")
+                "rivalName" to (repos.userData.findById(rivalId)()?.userName ?: "")
             )
         )
     }
diff --git a/src/main/java/icu/samnyan/aqua/sega/maimai2/handler/GetUserRivalMusicHandler.java b/src/main/java/icu/samnyan/aqua/sega/maimai2/handler/GetUserRivalMusicHandler.java
index 28be3c7b..3517828a 100644
--- a/src/main/java/icu/samnyan/aqua/sega/maimai2/handler/GetUserRivalMusicHandler.java
+++ b/src/main/java/icu/samnyan/aqua/sega/maimai2/handler/GetUserRivalMusicHandler.java
@@ -38,7 +38,7 @@ public class GetUserRivalMusicHandler implements BaseHandler {
         long userId = ((Number) request.get("userId")).longValue();
         long rivalId = ((Number) request.get("rivalId")).intValue();
 
-        List<Mai2UserMusicDetail> details = userMusicDetailRepository.findByUser_Card_ExtId(rivalId);
+        List<Mai2UserMusicDetail> details = userMusicDetailRepository.findByUserId(rivalId);
         List<UserRivalMusic> userRivalMusicList = new LinkedList<>();
         Map<Integer, UserRivalMusic> userRivalMusicMap = new HashMap<>();
         for (Mai2UserMusicDetail detail : details) {
diff --git a/src/main/java/icu/samnyan/aqua/sega/maimai2/model/Repos.kt b/src/main/java/icu/samnyan/aqua/sega/maimai2/model/Repos.kt
index 60319a59..cc4d061c 100644
--- a/src/main/java/icu/samnyan/aqua/sega/maimai2/model/Repos.kt
+++ b/src/main/java/icu/samnyan/aqua/sega/maimai2/model/Repos.kt
@@ -96,6 +96,8 @@ interface Mai2UserMusicDetailRepo : Mai2UserLinked<Mai2UserMusicDetail> {
     fun findByUserAndMusicIdAndLevel(user: Mai2UserDetail, musicId: Int, level: Int): Optional<Mai2UserMusicDetail>
 
     fun findByUser_Card_ExtIdAndMusicIdIn(userId: Long, musicId: List<Int>): List<Mai2UserMusicDetail>
+
+    fun findByUserId(userId: Long): List<Mai2UserMusicDetail>
 }
 
 interface Mai2UserOptionRepo : Mai2UserLinked<Mai2UserOption>