Tokyo Crazy Paradise (manga)

It's actually a manga.

A friend recommended this to me~

Promotion

In 2020, Tokyo has turned into a crime city. Women can no longer walk comfortably on the streets, drug dealers and thieves are everywhere. The Kozuki family, a police family, raised Tsukasa like a man to protect their daughter. However, Tsukasa's family lost their lives while investigating the death of the leader of the Kuryugumi, the largest Yakuza (mafia) family in the Kanto region. So Tsukasa stays on the street with his 3 brothers. With no one to turn to, Tsukasa goes to live with Ryuji, his classmate for 8 years and the son of the murdered mafia leader. Ryuji is the 3rd generation leader of the Kuryugumi group and someone Tsukasa hates for being a mafia. Desperate, however, Tsukasa lied to him, telling Ryuji that he saw the picture of those who killed his father, and thinks that he will lead a comfortable life for a while. However, the next morning, Ryuji takes Tsukasa's brothers hostage and forces them to tell the truth. The only way to save your brothers is to find the killers. Even though Tsukasa finds the killers, this time she faces the bill for her and her siblings' expenses. The only way to pay this bill is; Ryuji's new bodyguard is his bodyguard. (Excerpt from www.anime.gen.tr)