Yeah I don't like Reji and Masatsugu's plan. Yeah the Masatsugu's dad is evil, but I don't think what he does is any different than what the other Yakuza do. So if Reji manages to brings down the Masatsugu's father gang, it will just be replaced by an equally ruthless family. Yukio's dad was killed in inter-gang warfare, and Reji killed an enemy boss who was willing to enter into peace negotiations. More people like Yukios' dad will continue to die in the resulting crossfire. That's why I hope he dies in the end (after realizing how wrong his actions were), he's done too much harm to get a happy ending. He could've just killed Masatsugu's dad and left it at that.
And I'm not a fan of 'collateral damage'. Those who cause indiscriminate chaos and destruction to those other than the target (no matter how noble the cause), are just as evil as those they seek bring to justice.
It's difficult to know exactly what to root for in this story.
So many of the characters are so damaged and so many wires are crossed that I mostly want to see everyone move away to the country so they can start completely new lives. Except the boss/old man; he should die a really painful and humiliating death.