Kyourou wa Mayu wo Hamu

Kinuhime, the daughter of a yakuza boss, is to marry into a rival gang as an offering for their merger. Having to follow the whims of her parents, she loses sight of the meaning of life. When she meets Shian, the strongest and most ferocious of her bodyguards, she begins to shape her own destiny!

(Source: Shonengahosha, translated)

Note: Includes three extra chapters.