Tanjiro Kamado and Inosuke Hashibira vs Spider Demon (Mother)

Tanjiro Kamado and Inosuke Hashibira vs Spider Demon (Mother) was a battle that took place on Mount Natagumo. It focuses on the battle between Demon Slayers Tanjiro Kamado and Inosuke Hashibira against Mother of the Spider Family.

Prologue
After making a full recovery following their previous mission, Tanjiro Kamado, Zenitsu Agatsuma, and the newly joined Inosuke Hashibira head to the forests of Mount Natagumo for a new mission. But as night falls on the mountain and they reached the edge of the forests, Zenitsu became frightened by its creepy appearance and strange vibes, unwilling to continue. Near the edge of the treeline, a fallen Demon Slayer tries to call out to them but the three watch as he is suddenly pulled back into the forest. Deciding to take action, Inosuke takes charge of the mission and leads ahead; Tanjiro follows along to assist him while Zenitsu sits back on the road, too scared to continue. As the two enter the forest, they find it was strewn with spider webs and small spiders, confusing them. Eventually, after making a good distance into the mountain, the duo find another Demon Slayer, Murata. He explains that ten Demon Slayers of his rank were sent to the mountain; as they travelled through the woods, one of them suddenly drew his sword and slashed another member, killing him. Murata watched as his comrades began to kill each other without warning or reason, barely managing to escape the slaughter.

Battle
The three hear a rattling sound through the air, which Murata states is what was heard before the massacre began. Shortly after, they see the bodies of the dead Demon Slayers marching towards them. As they began to attack the three, Tanjiro notes that their movements are unnatural, believing they are being controlled. Inosuke's initial plan to kill them all is shut down when Tanjiro reminds him of the taboo of harming the corpses of fellow Demon Slayers. When Murata is pinned by one of them, Tanjiro and Inosuke help to get them off of him; Tanjiro senses a sweet scent and slashes behind the Demon Slayer, causing it to fall.

They discover that the spider webs they saw earlier are controlling their bodies, as well as the small spiders from earlier being the ones to attach threads of silk to them; with this in mind, Inosuke leaps above all of the Demon Slayers and rapidly slashes above their heads, freeing their corpses from the spider webs. No soon after this, they find a small child-like demon standing atop several webs, demanding they leave his family alone or "Mother" will kill them. Realizing there is something else at play, Inosuke uses his Beast Breathing, Seventh Form: Spatial Awareness and finds a demon hiding in the distance. Despite his earlier cowardice, Murata stays back to fend off all of the controlled Demon Slayers, now knowing to slash the threads and avoid getting hit. Thankful, Tanjiro takes Inosuke with him as they venture deeper into Mount Natagumo. Eventually, they discover the rest of the Demon Slayers; one of them is Ozaki, a female Demon Slayer who has killed each member of her squad. She begs for them to summon a higher ranking Demon Slayer or they will all die. Controlled by "Mother", she viciously attacks Tanjiro, swinging harder than she can on her own strength and her joints eventually snap as her ruthless puppeteer pushed her body beyond its limits. Another Demon Slayer appears to face Inosuke, his arms and legs horrifically broken and his bones piercing his internal organs. Begging for death, Inosuke offers to kill him but is denied by Tanjiro, who maintains that they can be saved. Thinking of a plan, Tanjiro runs away and sees that Ozaki is being forced to chase him. He then quickly turns around, empowers himself with his Total Concentration Breathing and pushes Ozaki high into the trees, causing the webs controlling her to get entangled and prevent her from being controlled. Inosuke, seeing this as a challenge and game, copies his actions. Eventually, they entangled all but one of the controlled Demon Slayers, preventing Mother from attacking them. Angered that her attacks are not working and under the threat of severe reprimand, she moves on to her new plan with a different doll and callously pulls on the threads attached to the Demon Slayers' necks. Tanjiro and Inosuke watch in shock as all of the Demon Slayers are killed before them. While Inosuke is annoyed that their efforts were futile, a silent Tanjiro releases his furious rage from seeing the murder of his comrades, startling the usually loud and confrontational Inosuke into silence. Tanjiro decides to move on ahead, as a quiet Inosuke agrees. Venturing even deeper into the mountain, they find Mother's strongest doll; a giant, headless demon with bladed arms as weapons. Without the usual weak spot of a demon to slice through, Inosuke asks how they can kill it; Tanjiro's solution is to slice it through the body from neck to waist. Inosuke charges ahead to try and slice through, sustain several minor cuts when the doll's blades catch him off-guard. At that moment, he forgets about avoiding the spiders and is suddenly restrained in place as the doll prepares to attack. Before he can get killed, Tanjiro parries the blow and saves Inosuke, cutting him free. After telling him of the importance to work as one, Tanjiro leads Inosuke in his plan, directing him to leap up off Nezuko's box. Inosuke jumps up and slices off both of the doll's arms, leaving it defenceless. As Inosuke watches the plan unfold as naturally as flowing water, Tanjiro uses Water Breathing, Fourth Form: Striking Tide and slashes off the demon's legs. Finally, Inosuke make the last cut, slicing through the body from neck to waist with both blades, successfully killing Mother's strongest weapon, shocking her.

Sensing the demon is near them, Inosuke runs towards Tanjiro, grabs him and hurls him high into the air. Initially surprised and confused, Tanjiro detects the scent of a demon below him, seeing it is the demon Inosuke had detected. Mother, now completely defenceless, panics and blames her failure on the pressure placed on her by Rui. Suddenly, she looks up and sees a Demon Slayer descending to kill her, Tanjiro, using Water Breathing, First Form for the final blow. Though she is initially scared, she realizes instead that she will be freed and know true peace. Releasing the threads from her hands, Mother surrenders completely. Seeing the demon is no longer showing anymore resistance, Tanjiro changes his grip; instead of using Water Surface Slash, he changes form and uses Fifth Form: Blessed Rain after the Drought, opting to use a strike to give the demon a peaceful end.

Aftermath
After getting struck by Tanjiro's blade, Mother notes that her death is not painful but feels like being showered by a gentle rain. She had never imagined that her death could be this peaceful and states she can now be released. She suddenly remembers when she was brutally punished for something she didn't even know what by Rui and her "husband", as other demons in her "family" watched.

Seeing Tanjiro's eyes and in awe at their kind appearance, she remembers that someone in her human life had looked at her once with the same expression, someone who loved her. As thanks for blessing her final moments, Mother warns the Demon Slayer that a member of the Twelve Kizuki is on Mount Natagumo, bidding him to be careful as she finally disintegrates completely.