Ataru is the older brother of Kinniku Suguru, the protagonist of the series, and the eldest son of the Royal Kinniku Family. In his childhood he could not endure the strict Spartan-like training his parents put him through and ran away from home. Because this all happened before Suguru's birth, Suguru was never aware of Ataru's existence. Ataru watched over his little brother from the shadows as he fought against Evil Choujin, making sure he learned the value of friendship, and then returned after 25 years during the Survivor Match for the Kinniku Throne.