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I think those who liked 'ichi the killer' or maybe some other yakuza manga's might like this. The twist with story though, is that the main character actually is very kind, but being a yakuza, has to put up a brave face. (But don't worry, he's actually strong, so it's not the type of story where everything is a coincidence and the Mc isn't actually strong) It moves on pretty quickly without dragging everything like most of the stories similar to this. Might be a little hard to comprehend.