In the sprawling metropolis of Gure-Tokyo, a city where delinquent high school students known as yankees have overrun nearly every school and teachers make up less than 0.2 percent of the population, a new force arrives. Chagecha, a towering figure with red dreadlocked hair, a white suit, scars on both sides of his nose, and a pair of glasses, returns to the city after a two-year absence. He lives inside a vending machine and wields a unique yankee special move called Human Motorcycle, a technique that involves pressurizing his own heart to unleash his true fighting potential. Chagecha is a third-year student at Gekinetsu High School, which was once a prestigious A-rank yankee school but has fallen to the lowest possible rank of D-rank after losing a brutal war against Nanrei Saiunkan High School two years prior, leaving only first- and second-year students. Determined to restore his school's tarnished name, Chagecha begins his campaign immediately upon return.

He quickly encounters Masato, a first-year student who becomes his loyal follower, and Himawari, a first-year girl who fights with a massive bowling-ball-shaped phone strap using her Mach-style attacks. Together with the remaining students of Gekinetsu High, including the quiet but dangerous Yoshiwara Kiyama who can become savage when provoked, the nine-year-old prodigy Doraji who uses a slot-machine-based special move, and the cowardly Longhorn Onizawa, Chagecha sets out to challenge the ruling yankee powers. The city is divided into ranked schools, with the top schools controlled by formidable leaders: the long-haired Hiiragi of Nanrei Saiunkan High, the chick-like Piyoppi of Uragaku Saimin High, and the sharp-eyed girl Ken Tomoko of Zaihayou High.

The first half of the story follows Chagecha's journey through the city, reintroducing him to the changed landscape of yankee politics. He learns that while he was away, the rules of combat have shifted. After finally reaching Gekinetsu High, a rank battle is initiated against a rival school, Red Storm High. The battle takes Chagecha and his allies underground into a tournament-style confrontation where his straightforward brawling style initially fails against the new, systemized fighting methods. Gekinetsu High is pushed to the brink, but Chagecha and his team manage to rally, using their absurd special moves in combination to turn the tide. In the final confrontation, Chagecha defeats the opposing leader and secures a victory for Gekinetsu High, successfully lifting the school's rank back from the lowest depths. The story closes with Chagecha laughing triumphantly, his mission to reclaim his school's honor complete, though the wider power structure of Gure-Tokyo remains largely unchanged. The single volume also includes a bonus one-shot titled Black Owl, which follows a ninety-year-old man named Kurosawa Houfukuro who transfers into a notoriously violent school to avenge a friend, dispatching ruthless delinquents with a calm, calculated brutality that contrasts with the main story's chaotic energy.