Gekiryuuchi

Kei is a high-school student who is bullied on a daily basis...and his classmates, teachers and parents don't seem to care. Pushed to his limits by the endless pain and humiliation, he accepts a strange proposal put to him by his childhood friend Akira; committing suicide together in order to end this nightmare.
The attempt fails -- Kei surviving and Akira disappearing without a trace.

Months later, Kei stumbles upon "Over Bleed" - a website on street fighting. Several videos on this site feature a barely recognizable Akira, now going by the nickname "Bunen", easily flooring scores of skilled opponents. Depressed and sickened by his own helplessness, Kei comes up with a reckless plan to discover the truth about his friend -- making his way from fight to fight until Bunen grants him a one-on-one battle...