Kyourou wa Mayu wo Hamu

A sheltered heiress of a yakuza clan is ordered to marry into an opposing gang to serve as a sacrificial offering for a merger between two clans. Trapped in a life predetermined by her surroundings, this girl encounters a beast-like bodyguard considered to be a "Mad Wolf" by their peers. As this sheltered girl witnesses this wild person's violent nature, her closed-off heart begins to stir.

(Source: Shonen Gahosha, translated)