Prince of Tennis: Kintaro Toyama's Cousin

Transmigration + tennis + underdog comeback + invincible + face-slapping + multiple heroines + playing dumb while hiding one's strength + scheming + big shots

Overworked 996 wage slave Koshin Kaito dies suddenly and transmigrates into the world of Prince of Tennis as Jiro Toyama, who lives under another family's roof. His parents disappeared when he was young, and he lives with his frail younger sister at his cousin Kintaro Toyama's home, where Kintaro bullies him constantly. After activating the Tennis Loser System, he begins his comeback, unlocking skills such as the reverse slice volley, Twist Serve, A and B smash shots, and the State of Selflessness (beginner level).

From defeating Kintaro and escaping the bullying, to beating Sato Aoi and Oshitari Kenya and gaining confidence, drawing with Echizen Ryoma in a street match, receiving guidance from Echizen Nanjirō, and running into Rikkai Dai's Sanada Genichiro while working a part-time job, Kaito's strength steadily grows. He also gets a chance to grow closer to Sato Aoi after rescuing her. Yet he is repeatedly crushed by the superior skill of Toyama Shigeru, Kintaro's father and a retired professional player, and Nanjiro, forcing him to recognize the gap between them.

Just before the school tryouts, an unexpected twist changes everything: While Kintaro is being put through brutal training by his father, desperate not to fall behind the protagonist, he unleashes a signature move from later in the story ahead of time: “Super Invincible Absolutely Delicious Giant-Wheel Mountain Storm.” He knocks Toyama Shigeru down. Kaito's hard-won comeback takes an unexpected turn, and the tryouts are full of formidable opponents and mounting suspense.