Yu Yu Hakusho - Season 2 Episode 20 : Hiei Battles On 1994

Yusuke is still in the midst of Genkai's Spirit Wave Orb absorbtion test. After a while, Genkai realizes that this is too much for Yusuke. She tries to take the orb back, but Yusuke takes it back. He wants to finish the test. Back in the ring, Shishiwakamuru rolls the dice. It lands on Kuro Momotaro and a free space for team Urameshi. Hiei volunteers to fight. Both fighters step in, and Kuro asks for Hiei's katana. Kuro licks the blade and cuts himself with it. The fight begins. Kuro pulls something called a steaming sphere out of his belt and squeezes it. Kuro inhales the fumes from the sphere and hair starts to grow from his body. This is the first beast armor, the Armor of the Ape. Hiei tries to attack with his sword, but it breaks in three pieces. Kuro gives him a few punchs and sends him into the wall. Kuro explains once his body is hit with an attack it memorizes the pain and steaming spheres are a catalyst to make his body immune to the attack.