Using the app

Keigo Companion is free to use, with no purchase required for any part of it. It's provided for personal Japanese-learning use, as a hand-authored, hobby-scale project — not a commercial service with an SLA.

Accounts

Signing in is entirely optional. Accounts are created via a passwordless email magic link through Supabase Auth — there's no password to choose or lose, but that also means access to your account depends on access to that email inbox.

Content

The verb bank, scenario bank, decision-tree reasoning, and nuance notes are hand-authored for this project. You're welcome to use them for your own study; they aren't licensed for republishing as someone else's material.

AI-generated explanations

The optional "explain why" feature on missed drill questions sometimes falls back to an AI-generated explanation (Claude Haiku 4.5) when a free rule-based check can't classify the mistake. Treat that explanation as a study aid, not an authoritative grammar reference — cross-check anything that looks off against the reasoning in the Decision Diagnostic or the Nuance Notes.

No warranty

The app is provided as-is, without guarantees of accuracy, availability, or fitness for any particular purpose — including the correctness of AI-assisted explanations. Deterministic grading (drills and scenarios) is checked against a fixed answer key, but language itself has edge cases; treat any single answer key as a strong guide, not gospel.

Changes and termination

This is a small, evolving project — features, scope, and these terms may change over time. You can stop using the app or clear your local data at any point. We may suspend accounts that abuse the free AI-explanation allowance or otherwise attempt to overload the service.