After revealing to Zenitsu that he has been poisoned and will begin to transform into a spider slave, the Son Spider Demon pulls out a pocket watch and begins to describe the different phases of his transformation.
He explains that within a span of a few hours, Zenitsu's hands and feet will begin to tingle, the feelings of dizziness and nausea will set in, followed by the feeling of intense pain, until his body finally shrinks and he loses consciousness. When he awakens, he will find that his body would have finished transitioning into a spider slave.
Zenitsu lets out horrified screams as the slaves crawl around his feet. He dashes away while openly admitting that he is already aware that running away will not help his situation, and ends up climbing a nearby tree.
Witnessing Zenitsu's episode of panic, the Son Demon laughs at him and reassures him that he has nothing to fear. Once Zenitsu finishes his transformation, he will no longer have a mind of his own or any sense of emotions. In response to his taunt, Zenitsu rambles saying that he doesn't want any of that and subtly insults him by saying "I bet you don't have any friends! People must hate you!", leaving the Son Demon glaring at him with spite.
As Zenitsu continues to cry about his fate, the scene flashes back to a similar situation when Zenitsu had climbed up a tree in the past. A voice can be heard sternly yelling at him to pull himself together, as Zenitsu squeals about his impending if he continues to train. The old man stubbornly calls him an idiot and tells him that it won't kill him, and commands him to get down from the tree at once. Zenitsu — with natural black hair — continues to wail, calling the old man "gramps", he cries out that he loves him and that he is eternally grateful for paying off his debt, but that he is simply not capable of training to be a swordsman.
He goes off on a tangent describing how he trains hard, but never sees any fruit to his labor and eventually lets out his anger at his failures. As Gramps tries to calm Zenitsu down an coax him down, a sudden bolt of lightning comes down striking both Zenitsu and the tree. Gramps looks on in horror as Zenitsu finally falls from the tree with his new striking blonde hair, bringing an end to the flashback.
Now back in the present, Zenitsu cries about wanting to change the way how he is in order to become a better person, and ultimately refuses to transform into a hairless slave. During his internal conflict, the Son Demon stares at him with utter confusion as his slaves climb up towards the tree to capture Zenitsu.
When he looks down, Zenitsu freaks out yet again as he notices the slaves approaching, and cries telling them not to approach him. He pulls on his head and suddenly pulls out a wad of his hair, Zenitsu stares at his hand in shock questioning why his hair was falling out when it was not a mentioned side effect. The trauma of having witnessing his hair falling out, causes Zenitsu to lose consciousnesses and he begins to fall from the tree.
As he descends to the forest floor, Zenitsu's subconscious takes control and he preforms Thunder Breathing: First Form - Thunder Flash to jump off the trunk of the tree and initiate his attack on the Brother Demon. In response to the sudden maneuver, the Son Demon spews his Blood Demon Art: Poison Sputum to try to deter Zenitsu, but he is able to evade his attack midair.
As Zenitsu lands on the ground he immediately attempts to utilize Thunder Breathing: First Form - Thunder Flash but is swarmed by an army of spider slaves. Zenitsu continuously dodges the efforts of the slaves and attacks from the Brother Demon, while trying to counter with the First Form, but the Son Demon figures out his inability to preform any other techniques.
Zenitsu thinks back to when Gramps had encouraged him that it was alright to only know one form. He shows feelings of extreme remorse in knowing that Gramps was furious about his inability to master the other five forms. However his barring actions were always to ensure that Zenitsu would never give up on his training.
The chapter comes to a conclusion when Zenitsu begins to prepare to preform a powerful attack citing that one must believe repetitive training will pay off, in order to become a "blade" stronger than anyone else.
Characters in Order of Appearance
- Zenitsu's backstory is revealed
- Zenitsu Agatsuma vs Spider Demon (Son) (Part 1)
- Kimetsu no Yaiba Manga: Chapter 33 (Page 4).