Been employed without a contact in hokkaido. Now the owner is refusing to pay out on the agreement

I've been managing a ski school in niseko this season. The boss is pretty sketchy, never provided me with a contract, promised x amount of working hours via email and is now saying he is not going to pay out the agreed upon amount.

I understand I'm probably screwed but I'm wondering if there's any laws that work in my favour about any of this? Honestly I've been doing this job in Japan for years and this is the first time a company has acted like this and I have no idea what to do.