diff --git a/frontend/domain/models/label/label.ts b/frontend/domain/models/label/label.ts
index ddcd9283..19416198 100644
--- a/frontend/domain/models/label/label.ts
+++ b/frontend/domain/models/label/label.ts
@@ -7,7 +7,13 @@ export class LabelItem {
     readonly backgroundColor: string,
     readonly textColor: string = '#ffffff'
   ) {}
-}
 
-export class DocTypeItem extends LabelItem {}
-export class SpanTypeItem extends LabelItem {}
+  static create(
+    text: string,
+    prefixKey: string | null,
+    suffixKey: string | null,
+    backgroundColor: string
+  ): LabelItem {
+    return new LabelItem(0, text, prefixKey, suffixKey, backgroundColor)
+  }
+}
diff --git a/frontend/domain/models/member/member.ts b/frontend/domain/models/member/member.ts
index bb40a18c..22e2326e 100644
--- a/frontend/domain/models/member/member.ts
+++ b/frontend/domain/models/member/member.ts
@@ -12,14 +12,4 @@ export class MemberItem {
   get isProjectAdmin(): boolean {
     return this.rolename === 'project_admin'
   }
-
-  toObject(): Object {
-    return {
-      id: this.id,
-      user: this.user,
-      role: this.role,
-      username: this.username,
-      rolename: this.rolename
-    }
-  }
 }
diff --git a/frontend/domain/models/option/option.ts b/frontend/domain/models/option/option.ts
index 8fc046e7..d28cc0b4 100644
--- a/frontend/domain/models/option/option.ts
+++ b/frontend/domain/models/option/option.ts
@@ -1,37 +1,3 @@
-export class PageNumber {
-  num: number
-
-  constructor(public page: number) {
-    if (typeof page === 'string' && /^\d+$/.test(page)) {
-      this.num = parseInt(page, 10)
-    }
-    if (typeof page === 'number' && page > 0) {
-      this.num = page
-    }
-    this.num = 1
-  }
-}
-
 export class OptionItem {
-  constructor(public page: number, public q?: string, public isChecked?: string) {}
-
-  static valueOf({
-    page,
-    q = '',
-    isChecked = ''
-  }: {
-    page: number
-    q?: string
-    isChecked?: string
-  }): OptionItem {
-    return new OptionItem(page, q, isChecked)
-  }
-
-  toObject(): Object {
-    return {
-      page: this.page,
-      q: this.q,
-      isChecked: this.isChecked
-    }
-  }
+  constructor(public page: number, public q = '', public isChecked = '') {}
 }
diff --git a/frontend/domain/models/tag/tag.ts b/frontend/domain/models/tag/tag.ts
index b1164f46..57a17d5a 100644
--- a/frontend/domain/models/tag/tag.ts
+++ b/frontend/domain/models/tag/tag.ts
@@ -1,11 +1,3 @@
 export class TagItem {
   constructor(readonly id: number, readonly text: string, readonly project: string) {}
-
-  toObject(): Object {
-    return {
-      id: this.id,
-      text: this.text,
-      project: this.project
-    }
-  }
 }
diff --git a/frontend/repositories/label/apiLabelRepository.ts b/frontend/repositories/label/apiLabelRepository.ts
index d9a87a9d..5be92b5c 100644
--- a/frontend/repositories/label/apiLabelRepository.ts
+++ b/frontend/repositories/label/apiLabelRepository.ts
@@ -2,16 +2,7 @@ import ApiService from '@/services/api.service'
 import { LabelRepository } from '@/domain/models/label/labelRepository'
 import { LabelItem } from '@/domain/models/label/label'
 
-export interface LabelItemResponse {
-  id: number
-  text: string
-  prefix_key: string
-  suffix_key: string
-  background_color: string
-  text_color: string
-}
-
-function toModel(item: LabelItemResponse): LabelItem {
+function toModel(item: { [key: string]: any }): LabelItem {
   return new LabelItem(
     item.id,
     item.text,
@@ -39,7 +30,7 @@ export class APILabelRepository implements LabelRepository {
   async list(projectId: string): Promise<LabelItem[]> {
     const url = `/projects/${projectId}/${this.baseUrl}s`
     const response = await this.request.get(url)
-    return response.data.map((item: LabelItemResponse) => toModel(item))
+    return response.data.map((item: { [key: string]: any }) => toModel(item))
   }
 
   async findById(projectId: string, labelId: number): Promise<LabelItem> {
diff --git a/frontend/repositories/member/apiMemberRepository.ts b/frontend/repositories/member/apiMemberRepository.ts
index 3ae8d119..7972511c 100644
--- a/frontend/repositories/member/apiMemberRepository.ts
+++ b/frontend/repositories/member/apiMemberRepository.ts
@@ -27,7 +27,8 @@ export class APIMemberRepository implements MemberRepository {
 
   async create(projectId: string, item: MemberItem): Promise<MemberItem> {
     const url = `/projects/${projectId}/members`
-    const response = await this.request.post(url, item.toObject())
+    const payload = toPayload(item)
+    const response = await this.request.post(url, payload)
     return toModel(response.data)
   }
 
diff --git a/frontend/repositories/option/apiOptionRepository.ts b/frontend/repositories/option/apiOptionRepository.ts
index c5eafb50..72965ed9 100644
--- a/frontend/repositories/option/apiOptionRepository.ts
+++ b/frontend/repositories/option/apiOptionRepository.ts
@@ -1,19 +1,32 @@
-import { OptionRepository } from '../../domain/models/option/optionRepository'
-import { OptionItem } from '~/domain/models/option/option'
+import { OptionRepository } from '@/domain/models/option/optionRepository'
+import { OptionItem } from '@/domain/models/option/option'
+
+function toPayload(item: OptionItem): { [key: string]: any } {
+  return {
+    page: item.page,
+    q: item.q,
+    isChecked: item.isChecked
+  }
+}
 
 export class LocalStorageOptionRepository implements OptionRepository {
   findById(projectId: string): OptionItem {
     const checkpoint = this.loadCheckpoint()
-    return OptionItem.valueOf(checkpoint[projectId] ? checkpoint[projectId] : { page: 1 })
+    if (checkpoint[projectId]) {
+      const option = checkpoint[projectId]
+      return new OptionItem(option.page, option.q, option.isChecked)
+    } else {
+      return new OptionItem(1)
+    }
   }
 
   save(projectId: string, option: OptionItem): void {
     const checkpoint = this.loadCheckpoint()
-    checkpoint[projectId] = option.toObject()
+    checkpoint[projectId] = toPayload(option)
     localStorage.setItem('checkpoint', JSON.stringify(checkpoint))
   }
 
-  loadCheckpoint() {
+  loadCheckpoint(): { [key: string]: any } {
     const item = localStorage.getItem('checkpoint') || '{}'
     return JSON.parse(item)
   }
diff --git a/frontend/services/application/label/labelApplicationService.ts b/frontend/services/application/label/labelApplicationService.ts
index 34dec0c9..6d2df156 100644
--- a/frontend/services/application/label/labelApplicationService.ts
+++ b/frontend/services/application/label/labelApplicationService.ts
@@ -17,26 +17,19 @@ export class LabelApplicationService {
   }
 
   public async create(projectId: string, item: CreateLabelCommand): Promise<LabelDTO> {
-    // Todo: use auto mapping.
-    const label = new LabelItem()
-    label.text = item.text
-    label.prefixKey = item.prefixKey
-    label.suffixKey = item.suffixKey
-    label.backgroundColor = item.backgroundColor
-    label.textColor = item.textColor
+    const label = LabelItem.create(item.text, item.prefixKey, item.suffixKey, item.backgroundColor)
     const created = await this.repository.create(projectId, label)
     return new LabelDTO(created)
   }
 
   public async update(projectId: string, item: LabelDTO): Promise<LabelDTO> {
-    // Todo: use auto mapping.
-    const label = new LabelItem()
-    label.id = item.id
-    label.text = item.text
-    label.prefixKey = item.prefixKey
-    label.suffixKey = item.suffixKey
-    label.backgroundColor = item.backgroundColor
-    label.textColor = item.textColor
+    const label = new LabelItem(
+      item.id,
+      item.text,
+      item.prefixKey,
+      item.suffixKey,
+      item.backgroundColor
+    )
     const updated = await this.repository.update(projectId, label)
     return new LabelDTO(updated)
   }