Qaos

I think the writer wanted to leave the reason in the air to make it more debatable.

Yes he killed him for sure. But even Ama said that sometimes he doesn’t understand what goes in his mind.

- could be he wanted the girl
- could be he was one of the Yakuza but he wanted to do it himself.
- could be (less likely) Ama wanted to die himself

I hate the ending so much. There was no justice! How could she live with a person like that!?

Ero overdose xD