I just want an easy-to-use offline AI chatbot that I can converse with in Japanese to practice with at native speed.

Does this not exist yet?

Me too! I couldn't find one so I cobbled one together. I wrote enough python for all the parts to work together. I can speak Japanese into it, it gets recognized, and - all too eagerly - the chatbot corrects my mistakes.

My stack, running locally on a Windows 10 machine: - Vosk STT augmented with vosk-model-ja-0.22 for Japanese - Gemma4 LLM running in Ollama and with customized model card to act as a Japanese tutor - Kokoro TTS using Japanese voice jf_alpha.pt and augmented with the unidic Japanese dictionary

Isn't it called Mistral Voxtral 3[1]

Not that I would trust an AI chatbot with Japanese. Most online text translators can barely cope with Japanese, DeepL is the only one that provides passable results. Its a tricky language.

[1] https://mistral.ai/news/voxtral-3/