Mobile app · AI
Aikaiwa: AI English conversation with characters you actually want to talk to
A mobile app for Japanese learners to practise speaking English with AI teacher characters, featuring real-time voice, pronunciation feedback and lessons by level. Launching in Japan in late 2026.
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Three AI teacher characters with real-time voice conversation
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Role-play lessons by CEFR level and an AI placement test
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Japan launch planned for late 2026
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The problem
Many Japanese learners know their grammar but rarely get the chance to speak, and practising with a person can be expensive or intimidating. The app's tagline puts it this way: "英語が、出てこない" (the English just won't come out).
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How we approached it
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Three teacher characters with different focuses: Sarah (daily conversation), Michael (business) and Emma (travel).
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Role-play lessons organised by CEFR level, an AI placement test, free talk, and streaks, quests and XP to keep learners coming back.
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A custom voice pipeline (speech to AI to speech) for natural back-and-forth conversation.
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Moved the app from a prototype tool (FlutterFlow + Firebase) to a maintainable Flutter + Supabase codebase, with a Japanese/English interface.
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Challenges we faced
Natural voice conversation
Speech recognition has to know when you've stopped talking. We added on-device recognition with fallbacks and noise filtering, and cached text-to-speech so replies start sooner.
Migrating without breaking the app
We moved the backend from Firebase to Supabase, with per-user data security, while keeping sign-in and user data working.
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