Sakura, a socially withdrawn otaku, saves a yakuza boss from harm and surprisingly ends up becoming his wife. The boss, who has three grandsons, challenges them to conquer Sakura's affection in order to determine his successor. "The one who wins her heart shall take my place," he proclaims. Despite their contrasting personalities, they are all resolute and skilled in their own unique manner; the eldest is delicate and tender, the second is notorious for his ferocity, while the youngest boasts of a versatile intellect.
