The manga I'm looking for is about the yakuza and it's not supposed to be comedy. There's this cop lady and she's trying to get evidence against this yakuza group, but in the end I think she falls in love with the yakuza leader and decides to help them (this isn't shoujo though). I remember at the end of the manga someone got shot or something but he survived... I know this isn't that specific but it's all I remember from it!

The ending sounds like GTO.

Nulla in mundo pax sincera
"Always go too far, because that's where you'll find the truth." - Albert Camus

Sanctuary, probably.