Professional Summary
Senior iOS Engineer with 7+ years building high-traffic consumer apps with UIKit and SwiftUI. Specializing in high-performance media rendering (e-book engines, image pipelines) and codebase modernization (Combine, Swift Concurrency). Strong focus on product quality through test infrastructure, CI/CD, and AI-assisted development workflows. Experienced collaborating across teams to ship user-facing features at scale. Active contributor to the mobile development community as co-organizer of Mobile Dev Japan.
Technical Skills
- iOS Native: Swift, UIKit, SwiftUI, Combine, Swift Concurrency.
- Architecture: MVVM, Clean Architecture, Modularization, SDK Design.
- Testing & Quality: Swift Testing, XCTest, Coverage Reporting (SonarQube).
- Perf & Tooling: Xcode Instruments, CI/CD (Fastlane).
- AI & Automation: LLM Integration (Claude Code), Automated Test Generation.
- Media Engineering: E-book/Manga Viewers (EPUB/Image), Vertical Reading Engines.
- Languages: Japanese (JLPT N1), English (TOEIC 930), Chinese (Native).
Professional Experience
LY Corporation (formerly LINE Corporation)
Tokyo, JapaniOS engineer for LINE's consumer and B2B apps, focusing on code modernization and production reliability.
- Delivered multiple features end-to-end utilizing MVVM architecture and Core Data, including LINE Touch (NFC-based friend adding), FanSpace x OpenChat integration, and message visual indicator system for OA chats.
- Designed, built, and demoed an on-device ML inference SDK using Core ML with integrated debugging tools for validation and performance monitoring.
- Led iOS modernization by migrating key flows from RxSwift to Combine and from callbacks to Swift Structured Concurrency, reducing risk in async codepaths and improving maintainability.
- Modernized testing infrastructure by migrating from Quick/Nimble to Swift Testing, strengthening test coverage, and introducing PR-level coverage reporting (SonarQube) to increase release confidence.
- Pioneered AI-assisted development workflows by introducing Claude Code for automated test generation, establishing templates and best practices that improved team velocity and code quality.
- Ensured platform reliability by resolving critical issues including an iOS 18 WKWebView system bug and a production deadlock on older devices (rapid rollback + fix).
LINE Manga
Tokyo, JapanCore engineer for Japan's largest digital manga platform, specializing in EPUB rendering engines, Realm database architecture, and media streaming optimization for high-traffic consumer apps.
- Re-architected the manga rendering engine (EPUB-based → optimized image streaming), achieving a 4x performance boost through parallel loading and caching strategies for seamless reading experiences.
- Built automated Realm database regression testing and a self-repair mechanism for corrupted user data, drastically reducing CS inquiries and enabling safe schema migrations.
- Reduced daily crash rates by 40% through systematic refactoring of legacy Objective-C/Swift code, including resolution of a critical Realm thread-safety issue (representing ~20% of monthly crashes).
- Optimized the "Bookshelf" feature by refactoring O(n²) algorithms, reducing memory usage to 1/10th (1.46GB → 136MB for 1500-item operations) and preventing crashes on older devices.