The battle between Shinobu Kocho and the Spider Demon (Girl) took place on Natagumo Mountain. It centres on the fight between Hashira Shinobu Kocho, an insect, and the girl Spider Demon.
Prologue
As the Spider Demon Girl escapes the struggle between Tanjiro Kamado and Rui, she is frightened that, because of Rui’s power comparison to her own, she will be unable to “defend his brother” and will be murdered by him due to the sun. She encounters Murata soon after, much to his astonishment. She quickly recognises him as a demon slayer and uses her Blood Demon Art: Acid Cocoon to catch him.
After all the time he spent fighting at Mount Natagumo, Murata is startled to find a Demon who has mastered the Blood Demon’s methods. He tries to stab and open the cocoon swiftly to get out, but it backfires. The Spider Demon Girl then says that escape is pointless because the cocoon, despite its softness, is quite robust. Murata notices a thick linden-green liquid regurgitating threads and steadily filling the cocoon inside. The Spider Demon adds that the liquid will erode his uniform first, but that his body would soon corrode as well, leaving just his blood and internal organs.
Shinobu Kocho appears from behind the Demon, noticing the threads coming out of his palms, wishing him a pleasant evening and remarking on the moon’s loveliness.
Battle
To avoid decapitating Shinobu, the astonished Spider Girl Demon rushes away fast. She uses her Blood Demon Art: Acid Cocoon to try to trap Shinobu, but Shinobu effortlessly dodges all of the threads and continues to close the gap between them. Shinobu continues to kick the Girl Spider Demon’s bicycle on the ground as she closes the gap between them. Shinobu deduces that the Spider Demon does not want to be his “friend,” prompting the Spider Demon to beg for his forgiveness. The Spider Demon warns her that until she kills the demon slayers or appeases “him,” he would brutally punish her. Shinobu “shows compassion for the demon and expresses her willingness to’save’ her.”
The spider demon’s daughter is taken aback by the fact that a demon slayer wants to “rescue” her from her phoney brother, and she questions Shinobu’s sincerity. Shinobu then responds that she has ask him some things in order for him to save her. The first is the amount of people she killed and consumed. The Demon Spider Girl responds with a five right away, but Shinobu sees right through her fake and tells her she doesn’t have to lie. The spider demon, on the other hand, stands by her statement that she killed five humans. Shinobu corrects her by telling her that she is from the Natagumo Mountain region to the west.Because she came from the west, she saw hordes of cocoons clinging to the branches, each containing a single human completely liquefied from within. From a single horde, she counted at least fourteen humans.
When the Spider Demon Girl inquires as to why she needs to know how many humans she has killed, Shinobu responds that she needs to be punished appropriately in order for them to be friends. Shinobu claims she could tear out his eyes, open his stomach and rip his insides out, and so forth. Shinobu encourages him to give it his all, assuring him that his mistakes will be forgiven. Shinobu, with his upbeat mood, encourages him that if he gives it his all, his mistakes would be forgiven. The spider demon, enraged and fearful of future torture, assaults Shinobu and seeks to capture her once more. Shinobu dodges it yet more, bemoaning the demon’s poor decision and untying his sword. Shinobu is seen jumping through the air towards her, surrounded by butterflies. Only one butterfly lands on the Spider Demon Girl’s right finger after dozens of butterflies pass in front of her. The butterfly then transforms into sculpted blood, causing his finger and entire chest to bleed. Shinobu attacks the Spider Demon Girl with his Insect Breathing, Butterfly Dance: Caprice.
The Spider Demon Girl checks her neck to see if she’s been beheaded, which she isn’t. She speculates on how and why the Insect Hashira didn’t behead her, concluding that Shinobu lacks the strength to behead a Demon. This is the primary cause for his Nichirin Blade being narrower than usual. Her own veins begin to break out and purple spots emerge on her skin as she prepares to assault Shinobu. His own wounds from Shinobu’s strike start streaming with blood, and his body begins to pain swiftly, while he is completely perplexed by what’s going on. By rapidly spinning his Nichirin Blade, Shinobu claims that no Demon is totally secure, even if not decapitated.
