hmm this thread couldn't have came up at a better time, i recently came upon this manga

Tokyo Crazy Paradise:

Kozuki Tsukasa parents are police officer that was recently killed while investigating a case,
leaving their 4 childrens homeless and in debt. Tsukasa has no choice but to seek help from a classmate name Ryuji who also happen to recently became the leader of the largest Yakuza group in the area because his father was assasinated. Ryuji was tricked into thinking that Tsukasa had seen the face of his father killer, one thing led to another and it end up with Tsukasa working for Ryuji as his body guard while Tsukasa is trying to get the family out of debt and become a Police Officer.

if you are interested in reading this it can be found here:
http://www.mangadownload.net/manga.php?a=series&sid=92

please refrain from reading the description on the website since it does spoil a little.