Fuyuhiko is the heir to the Kuzuryu yakuza clan. However, the clan believed he had no qualities of the yakuza and did not deserve the title. His younger sister, Natsumi, was considered by many to be much more worthy of the role. The Clan even believed she was the reincarnation of her deceased uncle who was known as the strongest Kuzuryu in history. She was given the chance to take her brother's place, but she declined due to caring about her brother. She didn't wish to lead the Clan, believing she was so amazing because she was Fuyuhiko's sister.
Along with having a good relationship with his sister, Fuyuhiko was also very close with Peko, albeit due to different reasons. Peko, abandoned as a newborn, was raised together with him since birth and served as his personal assassin.
Peko was always there by Fuyuhiko's side when he needed her. When Fuyuhiko's parents had their constant fights and few times nearly killed their own son in the aftermath of their fights, Peko protected him. When Fuyuhiko and Peko went to the zoo at one point when they were children, he challenged the king of the monkeys to a fight, and Peko had no choice but to join in the fray to protect him. She thought that Fuyuhiko had a handsome smile at that time. Fuyuhiko was also once kidnapped as a child along with Peko. They both succeeded in fleeing, but ended up getting lost in a mountain. Peko desperately tried to cheer up Fuyuhiko, but she ended making him cry because he could sense Peko's fear and anxiety, and because she was unfamiliar with smiling and showing similar warm emotions. However, they were finally saved because of Peko's ability as a swordswoman. Since Fuyuhiko was in 2nd grade, he no longer cried over anything, including losing a fight.
Fuyuhiko grew to dislike his reliance on Peko, as he was already considered weak among the yakuza and he hated it when Peko was treated as a mere tool. Furthermore, both Fuyuhiko and Peko appeared to have romantic feelings for each other, but neither confessed as their relationship was obviously complicated.
As a teen, Fuyuhiko attended Suzuran High School before enrolling in Hope's Peak Academy as the Ultimate Yakuza, in Class 77-B. Because he disliked crowding and being too familiar, he kept a bit of distance between himself and his classmates. Peko enrolled in the school with him, as the Ultimate Swordswoman, though they agreed they would act just like ordinary classmates.
During his time at Hope's Peak Academy, Fuyuhiko was potentially involved in a series of murders. His little sister was killed by a fellow student named Sato, who covered it up along with Mahiru Koizumi, blaming it on a serial pervert. As an act of revenge, Fuyuhiko killed Sato in the same way that she killed his sister Natsumi, hitting her in the head with a metal baseball bat, killing her instantly.
