How to force WhisperAI to use Japanese for transcription?

I am using whisperAi to transcribe a video. The thing is, the video contains some English as well, this causes Whisper to generate romanji instead of the actual japanese characters. How do I force it to always use japanese characters. The output currently looks like this

[11:05.500 –> 11:06.500] I should have stayed home.

[11:06.500 –> 11:08.500] Ireba yokatta.

[11:16.500 –> 11:18.500] Or I should have ran away.

[11:18.500 –> 11:20.500] Nigereba yokatta.

[11:30.500 –> 11:32.500] Nigereba yokatta.