One day, Sakura, an otaku shut-in, saves the life of the Amou-gumi's leader, and ends up becoming a yakuza's wife?! The leader declares to his three grandsons that, "The person who wins over Sakura-san will become the next leader"! The eldest son is weak but kind, the second son seems fierce and aggressive, and the third son is a level-headed intellectual. The three of them are all highly skilled and stubborn in their own ways...
(Source: Kodansha, translated)
