Tanjiro Kamado and Inosuke Hashibira vs Spider Demon (Father)

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

Prologue
Tanjiro faintly hears the sound of thunder and is perplexed as he does not smell nor see any thunderclouds anywhere in the sky, leading to him questioning why he heard the sound. Inosuke annoyed at the boy for wanting to treat/aid him answers with him having no idea. As the latter attempts to cross a tiny stream, Tanjiro asks him if he is descending down the mountain. This infuriates Inosuke even more with Tanjiro wanting him to as the former is heavily injured despite him not believing it.

Soon after they witness an incredibly pale-skinned girl on the other side of the stream with Tanjiro and Inosuke immediately recognizing her as a demon, even while Tanjiro couldn't pick up her scent due to the pungent odor all over the mountain. Inosuke immediately engages the girl with her screaming "Father!" which confuses the Demon Slayer, suddenly an enormous figure falls from above nearly crushing Inosuke which appears as a gargantuan man with dark-palish brown skin with long-silver white hair with the face of a spider which horrifies the two Demon Slayers. The "Father" Spider Demon yells at the two Demon Slayers to "Stay away from my family!".

Battle
The Father Spider Demon makes a huge punch towards Inosuke which he can't dodge. Tanjiro thankfully saves Inosuke by cutting the Demon's punching arm with the Water Breathing, Second Form: Water Wheel. The attack however did not cut through the Spider Demon's arm off nor does it budge a little. The Father Spider Demon tries to punch Tanjiro with his other arm but Inosuke stops the other arm himself. As the both of them struggle to cut the demon's arms, he pushes them both far away from him from just his scream alone. Tanjiro is stomped that not even a Breathing Form can cut through the demon's arm. Speaking of which, the Father Spider Demon sprints towards Tanjiro yelling at him to stay away from his family. Inosuke yells back and leaps at the demon to fight him, to which the Father Spider Demon smacks him far away. Inosuke is both shocked and admired over the sheer force of a single sweep of the demon's arm. The Spider Demon then sprints towards Inosuke with the latter running away down the stream. Running along with them, Tanjiro uses the Water Breathing, Second Form: Improved, Lateral Water Wheel to chop down a tree which in fact falls onto the Father Spider Demon.

This shocks and confuses Inosuke as to what and why that has happened with Tanjiro asking Inosuke if he is okay. With the Father Spider Demon stuck under the tree trunk, Tanjiro takes this opportunity to behead the demon with the most powerful form of the Water Breathing, thus unleashing the Total Concentration: Water Breathing, Tenth Form. The technique however was stopped before it even started as the Father Spider Demon got back up and lifted the tree trunk that fell on him. The tree trunk blocks both Tanjiro's attack and with the Father Spider Demon swinging the trunk sends Tanjiro flying far away from the battlefield.

Aftermath
At the end of the battle Tanjiro is separated from Inosuke by the Father Spider Demon. When Inosuke is about to be killed by the Father Spider Demon, Giyu shortly arrives and kills the Demon using the Water Breathing, Fourth Form: Striking Tide.