diff --git a/src/app/components/marktone.tsx b/src/app/components/marktone.tsx
index 9494af1b..f3fec650 100644
--- a/src/app/components/marktone.tsx
+++ b/src/app/components/marktone.tsx
@@ -33,7 +33,7 @@ interface MarktoneProps {
 
 interface MentionCandidateItem {
   type: DirectoryEntityType;
-  id: number;
+  id: string;
   code: string;
   name: string;
   avatar: string;
diff --git a/src/app/kintone/directory-entity.ts b/src/app/kintone/directory-entity.ts
index cb729ab7..fcf65201 100644
--- a/src/app/kintone/directory-entity.ts
+++ b/src/app/kintone/directory-entity.ts
@@ -25,7 +25,7 @@ export class DirectoryEntityTypeUtil {
 
 export interface DirectoryEntity {
   type: DirectoryEntityType;
-  id: number;
+  id: string;
   code: string;
   name: string;
   avatar: string;
diff --git a/src/app/kintone/kintone-client.ts b/src/app/kintone/kintone-client.ts
index 65c037a5..975a3006 100644
--- a/src/app/kintone/kintone-client.ts
+++ b/src/app/kintone/kintone-client.ts
@@ -236,12 +236,12 @@ export default class KintoneClient {
       requestBody,
     );
 
-    return response.result.entities.map((entity) => {
+    return response.result.entities.map(({ entityType, id, code, name }) => {
       return {
-        type: DirectoryEntityTypeUtil.valueOf(entity.entityType),
-        id: parseInt(entity.id, 10),
-        code: entity.code,
-        name: entity.name,
+        type: DirectoryEntityTypeUtil.valueOf(entityType),
+        id,
+        code,
+        name,
         avatar: "",
       };
     });
@@ -259,27 +259,33 @@ export default class KintoneClient {
       requestBody,
     );
 
-    const users = response.result.users.map<DirectoryEntity>((u) => ({
-      type: DirectoryEntityType.USER,
-      id: parseInt(u.id, 10),
-      code: u.code,
-      name: u.name,
-      avatar: u.photo.size_24,
-    }));
-    const orgs = response.result.orgs.map<DirectoryEntity>((o) => ({
-      type: DirectoryEntityType.ORGANIZATION,
-      id: parseInt(o.id, 10),
-      code: o.code,
-      name: o.name,
-      avatar: KintoneClient.presetOrganizationImageURL,
-    }));
-    const groups = response.result.groups.map<DirectoryEntity>((g) => ({
-      type: DirectoryEntityType.GROUP,
-      id: parseInt(g.id, 10),
-      code: g.code,
-      name: g.name,
-      avatar: KintoneClient.presetGroupImageURL,
-    }));
+    const users = response.result.users.map<DirectoryEntity>(
+      ({ id, code, name, photo }) => ({
+        type: DirectoryEntityType.USER,
+        id,
+        code,
+        name,
+        avatar: photo.size_24,
+      }),
+    );
+    const orgs = response.result.orgs.map<DirectoryEntity>(
+      ({ id, code, name }) => ({
+        type: DirectoryEntityType.ORGANIZATION,
+        id,
+        code,
+        name,
+        avatar: KintoneClient.presetOrganizationImageURL,
+      }),
+    );
+    const groups = response.result.groups.map<DirectoryEntity>(
+      ({ id, code, name }) => ({
+        type: DirectoryEntityType.GROUP,
+        id,
+        code,
+        name,
+        avatar: KintoneClient.presetGroupImageURL,
+      }),
+    );
 
     return new DirectoryEntityCollection({ users, orgs, groups });
   }
diff --git a/src/app/markdown/replacer/mention-replacer.ts b/src/app/markdown/replacer/mention-replacer.ts
index 778855b6..b04f56eb 100644
--- a/src/app/markdown/replacer/mention-replacer.ts
+++ b/src/app/markdown/replacer/mention-replacer.ts
@@ -30,7 +30,7 @@ class MentionReplacer {
     };
     return (
       code
-        .replace(/[ @%&'"<>*]/g, replacer)
+        .replace(/[ @%&'"<>*+]/g, replacer)
         // Escape Markdown syntax characters following a multi-bytes character.
         .replace(/(?<!\w)[ _~![\]|\\-]/g, replacer)
     );
@@ -107,7 +107,11 @@ class MentionReplacer {
       if (!entity) return match;
 
       const attrName = type ? `${type}-mention-id` : "mention-id";
-      const href = type ? "#" : `/k/#/people/user/${code}`;
+      const href = type
+        ? "#"
+        : code.includes("@")
+          ? `/k/guest/#/people/guest/${escapedCode}`
+          : `/k/#/people/user/${escapedCode}`;
       // LRO/RLO may be included in `name`. Therefore, it is surrounded by bdi element.
       return `<a class="${className}" href="${href}" data-${attrName}="${entity.id}" tabindex="-1" style="${style}">@<bdi>${entity.name}</bdi></a>`;
     };