Ep. 51: Sesshomaru learns the truth about Inuyasha's demonic nature while Inuyasha faces a moth yōkai
Aired on November 19, 2001

Sesshomaru visits Bokusen'on, a tree yōkai responsible for creating powerful sheaths, to uncover the origins of Inuyasha's transformation. Meanwhile, Inuyasha and his group encounter bandits harassing a local village. Inuyasha and Miroku are ambushed by Gatenmaru, a moth yōkai who traps them in a venomous cocoon with the goal of claiming the Tetsusaiga. When separated from the sword that suppresses his demonic blood, Inuyasha begins to shift into his yōkai form, altering his state as the conflict escalates.
Episodes
- Ep. 47 · Naraku struggles with Onigumo's heart while Kikyo faces death and Kagome watches from afar
- Ep. 48 · Kagome returns home after seeing Inuyasha embrace Kikyo, then confesses her feelings to him.
- Ep. 49 · Sango finds amnesiac brother Kohaku after demon attack on Shikon Jewel shard
- Ep. 50 · Inuyasha and Sango confront Kohaku while Kagura reveals memory erasure
- Ep. 51 · Sesshomaru learns the truth about Inuyasha's demonic nature while Inuyasha faces a moth yōkai
- Ep. 52 · Inuyasha destroys Gatenmaru but loses control after demonic transformation
- Ep. 53 · Inuyasha seeks Totosai to defeat Ryukotsusei and master the Tetsusaiga
- Ep. 54 · Inuyasha masters the Backlash Wave to defeat Ryukotsusei
- Ep. 55 · Shippo falls for Satsuki, who clings to a quartz shard, until her brother returns as a lizard demon.