The story centers around the life of a young boxer named Ryuuji Takane and his sister Kiku, who is his coach. Ryuuji and his sister both inherited their father's talent for boxing with Ryuuji inheriting his strength and techniques while Kiku picked up his talent for analysis and strategy. In the past, their father was a famous boxer. Ryuuji and Kiku went away from home to train and become famous in order to help their lonely mother. On the way to stardom, they have to defeat the strongest challengers all over the world.