Sunset Bancho

(from ebookjapan):

Chuji Akagi transfers to Kiso Junior High School and is noticed by the Bancho Rengo, a gang consisting of bancho from all over the school. Akagi, who had beaten a third-year bancho in his first year at his previous school, easily defeats the leader of the Bancho Rengo.

Tadaharu thinks he has conquered all the Bancho Rengo, but he discovers that there is still a great Bancho controlling them from the shadows.