He is a 15 years old Japanese boy who decides to make a choice that is to enroll itself to Lair Of Tigris for taking care of his sick mother. But during the training his mother dies and Mr. X picks him to assassinate tiger mask. Thus hatred of Ken for Naoto always grows more till wanting to face it in a crash to the last blood.

At the end, Naoto succeeds make Ken understand that who is the true bad one( Mr. X ). Thus Yellow Devil becomes an other inseparable friend of the Man Tiger. Injured person in the crash with a sicario of lair of Tigris will end (than in reality it is Great Tiger), that he will put end to its career of wrestling .