I feel uncomfortable with the generalizations the manga is making about foreigners. It reeks of xenophobia and racism.
It's also glorifying the yakuza as an important part of Japanese culture which needs to be revitalized and regrown.
I can't subscribe to the messages the manga seems to want to impart to its readers, but I admit that its portrayal of yakuza as a weakened and endangered Japanese cultural tradition is strangely compelling.