Worth a watch, but ultimately weak movie

It's a technically well-made film, all the actors give decent performances and it offers a unique look at the world of Yakuza from the outsider's perspective.

Now, why did I find it weak? It lacks something in its core to carry the movie - there's absolutely nothing remarkable about it save for maybe the setting. The story is fairly basic for a gangster movie. The characters are mostly generic. The protagonist is uncharismatic and boring, we know almost nothing about his motivations and [spoiler]after he kills his old war buddy in cold blood for no good reason[/spoiler] eventually it becomes hard to even care for him. Literally the only special and interesting thing about it is the setting, other than that there would be no particular reason to watch it.