Yay! My first manga *attempt*! ^^ Here is a summary of the story.

It’s a known fact that in any city, there are only the rich and the poor. Hirou Takehiko has had to realize that reality more than once. To survive, money must become his main priority. To do so, Hirou must now do the only thing he knows...underground street fighting. Putting his body on the line to make money, all for a better life for his sister, Hirou must also juggle his regular school life in the midst of all this.
From fights at school to the bloody streets, a world darker than anything imaginable is right in front of us. There is no one to save you...no matter how loud you scream or cry for help...blood and tears will fall onto the unforgiving pavement...Welcome to the Underground.