Shinobu Kocho vs Spider Demon (Daughter)

Shinobu Kocho vs Spider Demon (Daughter) was a battle that took place on Mount Natagumo. It focuses on the battle between the Insect Hashira Shinobu Kocho against Daughter Spider Demon.

Prologue
As the Daughter Spider Demon runs away from the fight between Tanjiro Kamado and Rui, she is heavily concerned that due to the comparison between Rui and her own power, she is not be able to "protect her brother" and will soon be killed by him from the sun. Soon after, she runs into Murata much to his surprise. She immediately discerns that he is a Demon Slayer and thus captures him with her Blood Demon Art: Acid Cocoon. Murata is deeply shocked that he found a Demon who has accessed Blood Demon techniques after all the time he has fought in Mount Natagumo. He quickly attempts to stab and slash open the cocoon to escape but it backfires. The Daughter Spider Demon then comments that it is absolutely pointless to escape due to the cocoon being incredibly durable despite its softness. Inside the cocoon, Murata sees thick lime-green liquid regurgitate out of the threads slowly filling up the cocoon. The Spider Demon sadistically explains that the liquid will at first corrode his uniform, but not long will his flesh then be corroded along and the only thing left will be his blood and internal organs. In which the Daughter Spider Demon smiles as she will soon consume his blood and possibly satisfy Rui and not be killed by him.

Suddenly, Shinobu Kocho appears right behind the Demon and remarks that the threads come out from her palms along wishing her a good evening and commenting about the beauty of the moon as well.

Battle
The startled Daughter Spider Demon quickly steps away from Shinobu in order for her to not behead her. She attempts to capture Shinobu with her Blood Demon Art: Acid Cocoon, but Shinobu gracefully dodges all the yarn and keeps closing the distance between the two. As Shinobu finally closes the distance between the two, she constantly bicycle kicks the Daughter Spider Demon onto the ground. Shinobu reflects that the Spider Demon doesn't want to become her "friend", to which the Spider Demon quickly begs for mercy. The Spider Demon evokes that if she doesn't kill the Demon Slayers or satisfy "him", he will punish her greatly. Shinobu "sympathizes" with the demon and openly admits that she will "save" her.

The Daughter Spider Demon greatly surprised that a Demon Slayer will "save" her from her fake brother and questions if Shinobu is being genuine. Shinobu then says that in order to save her she has to ask her a few questions. The first being how many humans she has consumed and killed. The Daughter Spider Demon responded with five as her immediate answer, Shinobu however sees through her ruse and tells her that there is no need to lie. The Spider Demon however sticks with her answer of killing five humans, Shinobu debunks her response by reminding her that she came from the west of Mount Natagumo. Because she came from the west, she saw hordes of cocoons hanging from branches, each containing a single human completely liquified from the inside out. From a single horde she has counted at least fourteen humans. Because of this, Shinobu approximates that she has murdered at least eighty humans. The Daughter Spider Demon asks her why she even needs to know how many humans she has killed, Shinobu responds that she needs to receive the proper punishment in order for them both to be friends. Shinobu states that she could either gouge out her eyes, slash her stomach to rip out her insides, etc. Shinobu with her gleeful demeanor tells her to give it her all and her sins will be atoned. Angered and feared by her future torture, the Spider Demon engages at Shinobu and attempts to capture her again, Shinobu dodges it again lamenting the demon's poor decision and unhinges her sword. Shinobu is seen high in the air leaping right towards her with numerous butterflies behind her. Seconds after, the Daughter Spider Demon sees dozens of butterflies fly pass her with a single one landing on her right finger. The butterfly then rots into molded blood bleeding her finger and entire torso. In actuality, Shinobu uses her Insect Breathing, Butterfly Dance: Caprice on the Daughter Spider Demon.

The Daughter Spider Demon immediately touches her neck to see if she was behead to which she was not. She questions as to how and why the Insect Hashira didn't behead her, to which she concludes that Shinobu doesn't have the necessary strength in order to behead a Demon. This is the main reason why her Nichirin Sword is even more narrow than normal. This greatly boosts the Spider Demon's confidence in defeating her, however as she was about to attack Shinobu, her own veins start popping out and purple spots appear on her skin. Totally perplexed on what is going on, her own wounds from Shinobu's attack start dripping more blood and her body begins aching rapidly. Shinobu then says that no Demons are completely safe even if they aren't beheaded as she spins her Nichirin Sword rapidly. She then explains that due to her being unable to effectively behead a Demon, both her and her Nichirin Sword swordsmith have created a special Nichirin Sword in which the scabbard injects Wisteria poison lethal to demons into their blood.

Aftermath
The Daughter Spider Demon dies shortly after taking in the Wisteria poison.