What should I charge per filled position as a freelance recruiter in Japan? (Commission-based salary)

I’m gearing up to start my freelance recruiting journey and have been approached by a recruitment agency interested in collaborating. They’re based outside Japan and are having trouble connecting with Japanese candidates, so they’re seeking my help for a few roles on a commission-only basis.

For those with experience in Japan (and even those from other areas), I’d appreciate your advice on fair pricing for this arrangement. They’ve mentioned about 5 open positions for me to work on.

I bring around 4 years of recruiting experience to the table and am fluent in both Japanese and English. Thank you!