Riki Hyoudo dreams of becoming the world's strongest fighter, and his journey begins by challenging his entire high school karate team. Wearing his signature leopard mask, Riki defeats the members one by one before taking down the imposing team captain, Baba. As he celebrates his victory, he encounters an unpleasant surprise: his fighting prowess has attracted the attention of Byoudo, Master of the Dark Realm. Now, Riki faces a barrage of opponents from both Earth and the Dark Realm, plunging his life into chaos. With his life at stake, Riki is compelled to rely on newly acquired powers that threaten his humanity.