Couldn't take protagonist seriously as he is supposed to be a fighter but from the fist shot it is obvious that he has never lifted a weight or even heard of a gym.
Regardless, the action is good and visceral.
The story is better than expected even if it has some wtf moments.
So if you just want some action with at least some quality this movie is well worth watching!
So to recap here are some things to improve upon:
Cinematography: most of the shots were generic with just a bunch of dudes walking around in obvious sets.
Please put more effort to cinematography, it can make or break a movie!
Also if someone is supposed to be an unstoppable fighter... he should look like one.
Finally, if you make an Yakuza action movie, the political side should be fast explained (like this movie did... in the beginning) Especially when everything eventually boils down to "KILL EVERYONE"
Anyway, watch it but don't think too much.