Several years ago, underneath a mansion, several rich people gambled on watching two genetically-engineered monsters called "Players" fight each other to the death. However, one day, the Players suddenly gained free will and slaughtered all the people inside. The only escapees involved a scientist and a baby, along with at least 15 Players.
In the present, a homeless boy named Jin lives with his equally-homeless grandpa, trying to act as a superhero like his friends while a mysterious serial killer known only as the "Wind Killer" is stalking the streets. He manages to save a pretty woman from some thugs in exchange for 10000 yen, but his friends Kouga and Konoha Amagi soon appear and drag him away, saying that a real hero shouldn't ask for payment. The woman meets up with Jin later and gives him the money and her business card anyways as thanks.
Jin returns to his grandpa's encampment, only to find everyone there is dead and no doctor will help. He tries to call Kouga but Kouga's father is furious that he is friends with the homeless boy and snaps his cell phone in half. So Jin turns to his last bit of hope, the woman who gave him the business card. He meets up with her at a hostess club, and she takes both Jin and his dead grandpa to a hospital. After realizing that he has no real family the woman (Akemi) offers to let him stay at her home for now.
The next night, while going on a stroll, both Jin and Akemi are attacked by the mysterious "Wind Killer." He injures both of them with his strange tongue and turns into a lizard-person, but when Jin sees Akemi hurt he transforms into a superhero and slams the killer into a wall, killing him instead. Two mysterious strangers deal with the corpse.
Later, Jin wakes up in a hospital, while a police detective suggests that he hang on to "hope." Jin asks him what that means, and he reveals the wounded but still-alive body of Akemi.