I build apps
and small tools.

Recent projects

Selected

Four apps, built solo.

Joshirushi: map view showing 255 castles across Japan Joshirushi: a goshuin stamp earned by visiting Himeji Castle Joshirushi: collected stamps shown in a personal album

01 — 2026

城印帳

A travel companion for Japanese castle hunters.

御城印を集める城巡りアプリ。

  • SwiftUI
  • SwiftData
  • App Clip
  • RevenueCat
  • Core Location

Released on the App Store in April 2026 — my first shipped app. The App Clip lets travelers check in at a castle without installing the full app, while the bundled dataset of Japan's 100 most famous castles stays under Apple's 15 MB limit.

On the App Store
Mentor AI: AI interviewer asks a real interview question Mentor AI: detailed feedback with score and improvement tips Mentor AI: growth tracking with score chart and weakness ranking

02 — 2026

Mentor AI

An interview reflection coach that never leaves your phone.

録音もAI分析も完全オンデバイスで動く面接対策アプリ。

  • SwiftUI
  • iOS Speech
  • Apple Foundation Models

Records practice interviews and turns them into structured feedback — without sending audio or text anywhere. AI analysis runs entirely on device via Apple Foundation Models. No data ever leaves the phone.

On the App Store
FitLoop: AI builds your weekly training plan in 20 seconds FitLoop: today's workout menu with exercises and sets FitLoop: growth tracking with weekly volume and muscle group trends

03 — 2026

FitLoop

AI personal coach that builds your weekly training plan.

AI パーソナルコーチが毎週あなた専用の筋トレメニューを自動生成。

  • SwiftUI
  • SwiftData
  • Google Gemini API
  • RevenueCat

Answer four questions and FitLoop's AI coach generates a full week of training. Log your sets, and the plan adapts next week based on your actual performance. All workout data stays on device.

On the App Store
CertLoop: home shows your pass-line gauge and today's 10 questions CertLoop: AI explains why you picked the wrong answer CertLoop: AWS service mastery ranking from S3 to CloudFront

04 — 2026

CertLoop

An AI study loop that pinpoints your weak spots — built for AWS SAA.

AI が毎日あなたの弱点を突く AWS 認定試験対策アプリ。

  • SwiftUI
  • SwiftData
  • Google Gemini API
  • StoreKit
  • Live Activities
  • Apple Watch

CertLoop reads your answer history, picks ten questions that target your weakest AWS services, and uses Gemini to explain why your wrong answer felt right. A 65-question, 130-minute mock exam mirrors the real SAA-C03 the moment you're ready.

Coming to the App Store

About

Independent. iOS-first.

I'm a solo developer based in Japan, working mostly on iOS. I shipped my first app on the App Store in April 2026, and I'm building three more — an on-device interview coach, an AI-powered workout planner, and an AWS certification trainer.

日本拠点のインディー開発者。iOS を中心にアプリと小さな道具を作っています。

Contact

Say hello.

email
yasudariku1214@gmail.com
github
@Yasuda-Riku