Shishito Shinobu, a 16-year-old with no skills other than fighting, starts a bare-knuckle fighting contest for 1 million yen in an attempt to ease the burden on his older sister, Misuzu, who has always looked after him. Shinobu boasts invincible strength and is undefeated. He was making some money and things were going smoothly, but then a hitman known as "Ashura" appears and the situation changes drastically...