Intro. Kento used to live in fear and trauma after his dad killed his older brother to sell his organs to the black market, sell his younger sister to the loan shark to pay his debt that then to be heard that his younger sister are being forced to work at the brothel to be a slave to those lustful and sinful creature that he could barely call 'human'. His dad die in a fire that were set up by a certain yakuza organization.
His reaction?
No, there's no emotion being shown at that moment but his word. - 'That scum, he deserve to be dead after what he did to Kenji and Kana'
His word pique an interest of the yakuza's leader, Yamazaki Hanzai who killed his father. Hanzai insisted on taking Kento as his child but that lil kid who only 7 years old, refuse to be part of the yakuza and so Hanzai respect that decision but to proof his determination in taking Kento as his child, he change Kento's family name from Kamata Kento to Yamazaki Kento before Hanzai himself send him to the orphanage.