Solo-built tools
for everyday work
Hakokit is a portfolio of small, focused tools — Japanese AI proofreading (校正AI), browser-native image/PDF/QR converters (画像ラボ), YouTube AI summarization (要約チューブ), invoice generation for Japan's qualified-invoice system (請求書メーカー) — each built to shave 10 minutes off a real workflow. Everything has a free tier, and the browser-only tools need no sign-up.
Catalog
What tools are available?
Every app in the Hakokit portfolio. Click a card to open the service.
- 文章ツールLive
校正AI
校正AI は日本語ビジネス文書を AI で自動校正するツールです。誤字脱字・てにをは・二重敬語の検出から、文体の統一・トーン調整まで Grammarly 水準の UX で無料から使えます。敬語辞典・業種別テンプレートも内蔵。
- AI 校正・リライト
- 敬語辞典 200 項目
- 業種別メールテンプレ
- 文字数・語彙カウント
- 画像・PDF ツールLive
画像ラボ
画像ラボはアップロード不要・完全ブラウザ処理の画像加工ラボです。画像圧縮 / HEIC 変換 / 背景削除 / PDF 分割・結合 / QR コード生成 / GIF 作成まで、ファイルを外部送信せずにその場で処理。無料・会員登録不要。
- 画像圧縮 / HEIC 変換
- 背景削除 (オンデバイス)
- PDF 分割・結合
- QR / GIF 生成
- 動画ツールBeta
SumTube
SumTube auto-summarises YouTube videos with Claude as a Chrome extension and web app. Three-layer output — one-liner, key points, and timestamped chapters — turns a 30-minute video into a 30-second read, with one-tap scene jump in-video. Free tier included.
- ワンクリック要約
- タイムスタンプ付きチャプター
- 日本語動画に特化
- 要約履歴と検索
- コンテンツツールLive
RepurposeAI
RepurposeAI converts a single YouTube URL or pasted text into X threads, Instagram captions, LinkedIn posts, blog summaries, and newsletters in one shot. Powered by Claude with platform-aware character limits, hashtag conventions, and tone-of-voice tuned for Japanese and English creators. Free 3-day Pro trial — no card required.
- YouTube → 5 媒体 一括生成
- X / Instagram / LinkedIn / ブログ / ニュースレター
- 日本語特化バイラル文体
- 3 日間 Pro 体験 (カード不要)
- 履歴書ツールLive
履歴書メーカーAI
履歴書メーカーAI は日本の転職市場に特化した AI 履歴書ジェネレーターです。JIS Z 8303 完全準拠の履歴書と職務経歴書を 60 秒で生成。職種別テンプレート、敬語・業界キーワード最適化、ATS スコア算出まで一体化。カード不要で 3 日間 Premium 無料体験。
- JIS Z 8303 規格 履歴書 PDF
- 職種別 職務経歴書 テンプレート
- AI 3 案提示 + 敬語最適化
- ATS スコア + 求人票解析
- 請求書ツールLive
InvoiceJP
InvoiceJP is a Japan invoice-system (qualified-invoice) aware generator. Automated T-number field validation, per-rate (8%/10%) consumption-tax breakdown, and withholding-tax calculation for freelancers, sole proprietors, and SMEs operating in Japan. Free tier: 5 documents per month.
- 適格請求書 (T+13桁)
- 8%/10% 軽減税率 自動
- 源泉徴収 自動計算
- PDF / メール即時発行
- 価格ツールLive
PriceWatch JP
PriceWatch JP unifies price histories across Amazon.co.jp, Rakuten Ichiba, and Yahoo! Shopping, auto-calculating effective prices that include Rakuten SPU rewards. Drop alerts, cross-store comparison, and AI-powered buy-timing make Keepa-class tooling available with the SPU layer Japanese shoppers actually use.
- 3 サイト横断追跡
- 楽天 SPU 実質価格
- 値下げアラート
- AI 買い時判定
- メール作成Live
MailCraft AI
MailCraft AI generates Japanese business-email replies tuned to the recipient relationship — five honorific levels, 50 scenario templates, and 3 variants per request. Available as a Gmail Chrome extension and a no-signup web playground. Where Gemini-in-Gmail and ChatGPT produce passable English, MailCraft handles the cultural specifics: seasonal greetings, double-keigo guards, formal-apology vs casual-apology vocabulary, and the polite closings Japanese counterparts expect.
- Gmail 拡張統合
- 5 段階の敬語レベル
- 3 案同時生成
- 50+ シーン別テンプレート
- 二重敬語自動チェック
Every Hakokit app, one plan
Use buncheck, sumtube, invoice-forge, resume-forge, tax-easy, tools, and the Hakokit dashboard for ¥4,980/month — the more apps you use, the more you save.
Normally ¥7,000/mo equivalent → ¥4,980/mo
- Access every Hakokit app
- One-click cancel · no surprises
- Qualified-invoice (適格請求書) ready
Or ¥49,800/year (≈ 2 months free)
What does Hakokit stand for?
Three principles that keep the portfolio coherent as new products land.
Try it free, first
Every tool has a free tier. 画像ラボ runs entirely in the browser with no sign-up; 校正AI lets guests try AI proofreading without an account. You never hit a paywall before experiencing the product.
Hold the minimum data, no more
画像ラボ processes images and PDFs entirely in the browser — nothing touches a server. 校正AI sends only the minimum text required for the AI check and never uses it for training. Harvesting personal data is not the business model.
Built to outlast the hype cycle
Solo dev means long time horizons. Browser-only tools (near-zero server cost) and AI tools (usage-priced) are kept architecturally separate so the portfolio doesn't depend on subscription inertia — you can always pay only for what you use.
友田陽大
Indie Software Engineer / Hakokit
日本を拠点に個人開発に取り組むソフトウェアエンジニア。日本語 AI 校正「校正AI」、ブラウザ完結の画像 / PDF 変換「画像ラボ」、YouTube AI 要約「要約チューブ」、インボイス制度対応の請求書ジェネレーター「請求書メーカー」など、Hakokit のすべてのツールを一人で設計・開発・運用しています。
Frequently asked
Common questions from people meeting Hakokit for the first time.
What is Hakokit?
Hakokit is an indie-developer's portfolio of productivity tools: 校正AI (formerly BunCheck) for Japanese AI proofreading, 画像ラボ (formerly Convert) for browser-native image and PDF conversion, 要約チューブ (formerly SumTube) for YouTube AI summarization, 請求書メーカー (formerly InvoiceForge) for 適格請求書-compliant invoice generation, and more — each built around the moment a real workflow can be 10 minutes shorter.
Are Hakokit tools free?
Every tool has a free tier. 校正AI gives unpaid users a daily quota of AI checks; 画像ラボ offers unlimited image compression and PDF merging without even a sign-up. Advanced features are paywalled, not the entry point.
Do I need to register?
画像ラボ needs no account — every feature works for anyone who loads the page. 校正AI has a guest mode too; an account is only needed when you want history or team sharing, signable via email + password or social login.
Are the files I upload stored on a server?
画像ラボ is purely client-side — nothing ever leaves your browser. 校正AI sends text to the Anthropic API for the check, but Anthropic does not train on it and the text is discarded after a short retention window. Each app links its full privacy policy.
Who runs Hakokit?
Hinata Tomoda runs Hakokit solo. It's not a team or a company — one person handles design, development, and operations. For questions, use the /contact form on any sister app.