Episode 172

The Great Holy Demon Spirit's Test is the 5th episode of InuYasha: The Final Act.

Plot
While Kohaku joins up with Kikyo, Koga decides to leave his lackeys behind from now on because of the danger. Sesshomaru meanwhile watches as Moryomaru tricks two demons and absorbs them both, and afterwards, he challenges him to a fight with his own new ability. Moryomaru, however, gets away and Sesshomaru isn't able to chase him because Byakuya distracts him.

At around this same time, Inuyasha has to deal with the fact that he can't handle Tessaiga's new ability, so he has Totosai take a look at it, and he sends Inuyasha to train with his acquaintance Yourei Taisei. When they reach the Yourei Taisei's place, they find that the old man has gotten his innards taken by a demon, and it thus becomes Inuyasha's job to recover them. To make things harder, Yourei Taisei puts a seal on Tessaiga to prevent Inuyasha from using it against just any demon. The group ends up at an isolated residence where they encounter a serpent demon, and although he still can't use Tessaiga, he is able to use his own claws.

After Yourei Taisei advises Inuyasha to look for the demon vortex, he is able to see the swirls of demonic energy. He's eventually find the right one and slashes it to destroy the serpent demon. However, this turns out to not have been the demon that took Yourei Taisei's innards, and when the group returns to Yourei Taisei's dwelling, they find an ox demon there. Inuyasha is finally able to use Tessaiga again, but he still have to find the right demon vortex, and even worse, cutting the ox demon cracks Tessaiga. Inuyasha, however, figures out that the real demon vortex is centered around Yourei Taisei's body, and in one swing ends the battle. In the aftermath, Yourei Taisei reveals that all this had been a part of his plan to retrain Inuyasha to be able to detect the true demonic energy and so that he would and so that he would remember that Tessaiga is a sword for cutting. Tessaiga is also now bathed in a great amount of demonic energy because InuYasha had cut Yourei Taisei's demon vortex, but what Yourei Taisei doesn't tell Inuyasha is that the Tessaiga has one more form to discover.