Yakuza Fiancé: Raise wa Tanin ga Ii

If it weren't for the fact that Yoshino Somei is the granddaughter of the head of the Somei Group, the biggest yakuza organization in the Kansai region, centered in Osaka, she would have been an ordinary high school student. When Yoshino learns one day that the Somei and Miyama groups, the two largest syndicates in Kanto have united, she rushes home. The story claims that this will lead to the grandchildren of the leaders getting married, including Yoshino herself! Yoshino is forced to travel to Tokyo to see her fiancé, Kirishima Miyama, who is surprisingly kind and charming, despite her best attempts to cancel the arrangement. After meeting, Yoshino gets entangled in a series of circumstances that make her want to move to Tokyo and, six months later, she's living with the Miyama group. She quickly learns that Kirishima is highly well-liked at school, and as a result, her friendship with him incites the wrath of his fangirls and leads to bullying. Adding insult to injury, Kirishima was born into a yakuza family, thus he was the furthest thing from her ideal partner.