Tanjiro Kamado and Nezuko Kamado vs Rui

Tanjiro Kamado and Nezuko Kamado vs Rui was a battle that took place on Natagumo Mountain. It focuses on the battle between Demon Slayer Tanjiro Kamado, and Nezuko Kamado against Lower Rank 5 Rui.

Prologue
Tanjiro tells Rui that he doesn't have a real family bond, only a fake one made out of fear, mistrust and violence, and not a bond made of love, kindness and compassion. This enrages Rui who then attempts to cut Tanjiro to pieces with his threads. Tanjiro dodges the steel-like threads to his best efforts. Rui then surrounds Tanjiro with a barrage of threads. Tanjiro closes his eyes, expecting to be cut up, but he was unharmed.

Both Tanjiro and Rui are surprised, as its revealed that Nezuko was the one who protected Tanjiro from the threads, while letting her body receive the full cutting force of the threads. Tanjiro screams Nezuko's name in horror, and then he quickly carries her to safety. Rui realizes that the two are siblings. He is shocked that even though Nezuko was a demon, she still protected Tanjiro, a human. Rui realizes that their bond was genuine. He declares that he wants that bond, his eyes shining with envy.

The Spider Demon Daughter, who was listening to this, begs Rui not to abandon her, as she was his older sister. In response, Rui cuts off the daughter's head, telling her to shut up. He then says coldly that she and everyone else in the "family" never fulfilled their roles, not even once. He then tells the daughter if she wanted to prove her worth to him, she should go and kill all of the Demon Slayers on Natagumo Mountain. The daughter obeys, then picks up her head, and leaves the scene. Rui then attempts to negotiate with Tanjiro, saying that he was really moved by Tanjiro and Nezuko's bond. Rui then says that he will let Tanjiro leave alive, but only if he lets him take Nezuko. Tanjiro immediately says no, saying that Nezuko is a living being with feelings, emotions, and a heart. Rui then says it would be alright, saying that he will forge a bond of fear between him and Nezuko. Tanjiro declares he will never hand over Nezuko, and that he will sever Rui's head. Rui compliments Tanjiro on his spirit and courage. He reveals to Tanjiro that he is actually Lower Rank 5 of the Twelve Kizuki. Rui then says he would like to see Tanjiro try to defeat him in battle.

Battle
Rui uses his threads to pull Nezuko over to her side, saying now that he had his sister, Tanjiro's role was to die. Tanjiro then charges straight at Rui with his broken Nichirin Blade. Rui uses his threads to attack Tanjiro while Nezuko attempts to escape from Rui's grasp, even clawing at his face. As Tanjiro dodges Rui's attack, he notices that Rui isn't holding Nezuko anymore. Just then, a spurt of blood falls on Tanjiro's blade. He looks up and sees Nezuko strung up midair by Rui's threads, with the threads digging into her skin, badly wounding her. Rui says that the threads won't kill Nezuko, since she's a demon, but she'll have to be taught a lesson. He continues to say that if Nezuko doesn't behave, he will leave her like that until sunrise to be burned and disintegrated. Tanjiro yells at Rui, demanding that he let Nezuko go. Rui then uses his threads to trip Tanjiro and make him collapse to the ground. He then kicks Tanjiro in the stomach which sends him flying to a bush.

Rui then beats up Tanjiro, and this continues until Tanjiro gets a chance to cut Rui's head off. But his blade doesn't even scratch Rui's neck. Rui declares that Tanjiro has no chance of defeating him, and he then gives another kick to Tanjiro, making him crash into a nearby tree. Nezuko who was witnessing this struggles in her strung-up state, screams and attempts to break free from the threads. Rui says she's making too much noise, and then he tells her to quiet down. The threads tighten and cut deeper into Nezuko's flesh, causing her to scream in pain as she becomes even more injured. Tanjiro then telepathically, tells Nezuko not to get emotional, or she would be playing right into Rui's hands. Nezuko then seemingly falls into a sleep-like state. Rui notes that Nezuko has a unique aura and is different from other demons. Tanjiro tells himself to calm down and to control his breathing. He realizes that in order to defeat Rui, he must use the final form of the Water Breathing. Tanjiro uses Water Breathing: Tenth Form - Constant Flux. Rui thinks to himself that if this continued, he would be in trouble. Rui then pumps his own blood into his threads, turning them red and increasing the power to his absolute limit. Tanjiro can tell by the scent of t