Rengoku Shin'enken (煉獄深淵拳, literally meaning Purgatory Abyss Fist) is a unique, highly extreme and unorthodox fighting style developed by Osamu Otsutsuki after in-depth study of several unique styles of Taijutsu and Ninjutsu. Due to it's "excessively dangerous nature", it was labeled a Kinjutsu. This style of taijutsu calls for a well trained mind and body and flawless control over the two.