Mastermind Japanese
Practical Japanese study that adapts to your current level and pushes you forward one concept at a time. Built for busy learners who want real N5 progress, not random drills.
Beta access is live. Core N5 study is open now.
Mastermind Japanese is a web app by Jason Kobayashi in Tokyo, built for busy learners starting with JLPT N5.
Why This Feels Different
Concept-Level Diagnosis
Miss a sentence? Mastermind isolates the exact concept, vocab, particle, or conjugation instead of marking the whole question wrong.
Prerequisite Awareness
The system understands dependencies. You build foundations first, then move into harder patterns at the right time.
Short Session Friendly
Designed for real life. You can do meaningful progress in short bursts without losing the learning thread.
How It Works
Start learning right away
Answer a few questions. Mastermind estimates your current concept strengths.
Practice at your frontier
Questions adapt to what you know and what you are ready to learn next.
Track N5 readiness
See your concept progress over time and keep momentum toward practical Japanese fluency.
Beta access
Join the beta
Beta access liveTry the current beta build with core N5 concept access.
- Adaptive study engine
- Core N5 concept access
- Session progress tracking
Officially supported on iPhone 12 or newer, iPad, Windows, and Mac. See all supported devices
Practice Stack
What You Train With
Updates are added regularly based on user feedback and roadmap priorities.
Product Facts
- Mastermind Japanese is a Japanese learning web app built by Jason Kobayashi in Tokyo.
- It adapts practice based on concept-level progress rather than random drills.
- The first live version focuses on JLPT N5 with 160 concepts and 577 curated questions.
- The product includes adaptive study, Kanji Foundations, Verb Focus, vocabulary flashcards, and a Mind Map.
- The current beta is free and open now.
© 2026 Jason Kobayashi