Episode 122

The Power of Banryū: Duel to the Death on Mt. Hakurei is the one hundred twenty-second episode of the InuYasha anime.

Synopsis

 * 1) Bankotsu destroys his thousandth yōkai, giving his Banryū its ultimate power.
 * 2) However, doing so caused Bankotsu's blade to emit a demonic aura, making him susceptible to Inuyasha's Bakuryūha, which Inuyasha uses, finally defeating the leader of the Shichinintai.

Summary
After being sent falling into a chasm by Kagura, Miroku and Sango survive, with Sango sticking her boomerang into the wall and hanging onto Miroku with a rope. At the bottom of the pit they find the remains of worm demons that Naraku has used to regenerate from his previous defeat.

Inuyasha continues his fight with Bankotsu, before the latter pins Inuyasha to a wall intending on finishing the fight before he derides him as a weakling. He then goes for the kill. However, Inuyasha removes three Jewel Shards from Bankotsu's neck, he tells the shocked Bankotsu that he isn't like all those other humans or demons he's slaughtered. Inuyasha reveals he intentionally got hurt as he proclaims he can take a lot more damage than Bankotsu's victims before kicking him away. He states he has five shards, leaving Bankotsu with only two left. Inuyasha notices Naraku's demons watching on the sidelines, and tells Bankotsu that they will try to kill whoever wins the fight and that Naraku has been using Bankotsu, since he intends to take all pieces of the Shikon Jewel. Bankotsu says, being a mercenary for warlords he knew Naraku was using him all along, and doesn't care, as he is confident that he can kill Naraku.

Bankotsu grabs Banryū and kills enough of Naraku's demons that he has killed a thousand demons with Banryu (much like he has killed a thousand humans already), increasing Banryu's power and giving it a demonic aura. Ironically, this allows Inuyasha to use the Backlash Wave, destroying Banryu and finally defeating Bankotsu. Inuyasha tells a dying Bankotsu that he was way too greedy as he was strong without the shards as Bankotsu laughs in acknowledgment of his overlooked mistake before passing on.

The cave they are in starts to turn to flesh, and swallows Bankotsu and Inuyasha. Kōga is also swallowed after telling Kagome to stop trying to pull him free (realizing if she doesn't stop there's a good chance she'd be pulled in as well). Kagome, Shippō, and Kirara reunite with Miroku and Sango.