From SRoMU:

Kei is a high-school student bullied daily and none of his fellow classmates care. Worn down by those endless humiliations, he accepts the strange proposal of his childhood friend Akira : Suicide together to end this nightmare. But that day, Kei survives and Akira doesn't.

Months later, the young man is shocked when he discovers on the net a website about street fighting. On several videos put online, a barely recognizable Akira gives a major beatdown to his opponents! What really happened? To discover the truth, Kei has only one solution: registering on that site and go from fight to fight to find the truth about Akira...