From Tokyopop:

Chiyoharu used to be the leader of the troublemakers, until one day an innocent prank results in a major fire at the school. When his three cohorts take the blame and are expelled, Chiyoharu tries to go on with his mundane life, beating himself up with guilt. Then he meets the mysterious, muscle-man Souza of the North Wind and a ditzy self-proclaimed detective who are trying to solve the mystery behind Souza's amnesia...It's nonstop comedy and action from there!