As he is consuming a group of his female disciples inside Nakime's Infinity Castle, Doma notices Shinobu at the entrance to his room. He reacts with delight at having another meal walk right into his room, and thanks Nakime. One of his disciples, still alive, begs Shinobu to save her, and Doma, irritated by this, attempts to finish her off, only for Shinobu to jump in and save her. She asks the young woman if she is alright, but before she can answer Shinobu's question, the young woman explodes and dies right in front of her eyes.
Angered by this, and Doma's insistence that he saved the girl by killing her, Shinobu notices a pair of sharp fans that Doma uses as his main weapon, and angrily inquires if he remembers the haori that originally belonged to her elder sister. Doma finally remembers her by the butterfly wing design haori that Kanae once wore, and playfully expresses his disappointment at not being able to eat Kanae due to the sun rising, which further angers Shinobu.
The Insect Hashira swiftly launches an attack at him using her Insect Breathing, Dance of the Bee Sting: True Flutter to inflict a powerful stab directly in Doma's right eyeball, which impresses him since he couldn't block it.
Although he is initially dismissive of her, since he correctly guessed that she lacks the physical strength to cut off a Demon's head, he becomes excited upon learning that Shinobu's true strength lies in poisoning her opponents. Shinobu hopes that the poison will be effective enough to kill him, but then learns, much to her disappointment, that Doma had already received information regarding her poison from her battle against the Older Sister Spider Demon of the Spider Family. Doma manages to break down and render her poison non-lethal, healing himself from her attack. She is further backed into a corner due to Doma now rapidly developing antibodies and adjusting his body against her poison so that, after a mere five slashes and injections of poison, he is now resistant to it entirely. Also, due his Blood Demon Art of frozen mist, it's becoming increasingly difficult for Shinobu to breathe.Now hedging her bets on injecting a large dose to kill him by using a six stab attack, Shinobu strikes him using Insect Breathing, Dance of the Dragonfly: Compound Eye Hexagon and successfully hits him. However, as she attacks him, he simultaneously attacks her, cutting both her collarbone and ribs and puncturing one of her lungs. Finally near her wits' end and almost losing any hope of victory, Shinobu attempts to draw strength from replaying her older sister's words of encouragement in her head. Shinobu then prepares to strike at Doma again, despite her serious injuries and the immense pain she was in, and attacks him using Insect Breathing, Dance of the Centipede: Hundred-Legged Zigzag to confuse him. She strikes Doma directly through his neck, impaling him and sending him flying towards the ceiling. Exhausted and wounded, Shinobu is triumphant upon seeing Doma being poisoned and seemingly dying from her attack.
However, Doma recovers almost instantly from her attack, by which Shinobu is further enraged. Now exhausted, fatally injured and dangerously near death, Shinobu is caught by Doma as they were fall down from the ceiling. He embraces her in a bear hug, and begins mocking her and calling her entire attempt to defeat him a waste of effort, assuring her she will live peacefully as a part of him, and mockingly asking her for her last words. She spitefully curses him as as he begins to kill her.
In the end, she is absorbed by the Upper Rank, just as her disciple Kanao Tsuyuri arrives at the scene, but just before her death she manages to signal to her Tsuguko with her hand. Her death causes Kanao to go berserk in order to try and save her, only to be repelled by an irritated Doma, who tells her not to interfere when he's in the middle of absorbing someone. He successfully devours Shinobu's body until her butterfly-shaped hair piece is the only thing left of her.