The Umehoshi-Gumi was born on the year the Umehoshi Brothers enrolled at Suzuran. After the siblings' attack on the third year Kuroi, they immediately made a lot of enemies among their upperclassmen. Days and days of attacks led the rest of Suzuran's first years to rally under the Brothers to form the Umehoshi-Gumi. Due to their size and influence, the Umehoshi-Gumi looked poised to take over Suzuran, but that dream faded once the Brothers began engaging in arguments to determine who the better sibling was.

The core members of the Family include Yasushi and Masashi's childhood friends such as Yashiro Keiji and Mori Yoshio, as well as their underling, Aoki and Sugimoto.