To be sure, there is a little bit of ultra violence in the movie, but its emphasis and heart does not lie on or in Takeuchi's exploits as young Ginji, but on and in Isao Natsuyagi's fifty years older, broken Ginji, a walking dead in every but the literal sense.
Most of the time, yakuza vengeance films eschew ambiguity as much as possible, Ginji actually thrives on it, heavily helped by Natsuyagi's impressive portrayal of a survivor, a broken man who's just not broken enough to go through with dying or senseless vengeance. The ambiguity that drives the film also encompasses its use of the fantastic and the uncanny. Some of it externalizes Ginji's inner turmoil and the (not incredibly clear) political metaphors, none of it is explained away (or explained at all, for that matter).
The direction of the film is solid throughout and as competent as one can expect of a film made on a shoestring budget like this. As is to be expected, not every actor here is as nuanced as Natsuyagi or as charismatic as Riki, but I didn't find anyone distractingly bad.
The script is as ambitious and ambiguous as if written directly for me, only some small moments of melodrama late in the movie fall a little flat.
I give the movie 4.5 out 5 depressed moments culminating in violence.