Afterwards, Inosuke—who was still an infant at the time—and his mother were taken in by Doma into his Eternal Paradise cult. Kotoha loved to sing to Inosuke but would apparently change the song lyrics each time. However, after finding out that Doma ate his worshippers, Kotoha fled with her son. Running aimlessly for a human village, Kotoha eventually ended up at the top of a cliff. Seeing no escape route, she made a last-ditch effort to save Inosuke by dropping him into the river below the cliff. She was then devoured by Doma. Later on, Inosuke was discovered and raised by the boars.
While Inosuke does participate in the Final Selection at Mt. Fujikasane, he is off-screen for the entirety of the arc. His presence is hinted by Kagaya Ubuyashiki, when a crow tells him the results of the selection.
Inosuke had wandered into the Kyogai's Drum house presumably looking for demons to kill in order to become stronger, but due to the nature of Kyogai's blood demon arts, ended up trapped for 3 days. He first appears when Zenitsu and Shoici are searching for an exit, having been separated from Tanjiro and Teruko. Zenitsu slides open a door which he believed was the exit, and desperately opens another when the first door fails. Behind that door is Inosuke, who immediately hurtles out and knocks down another door before running down the opened corridor. Zenitsu is left shakened, with Shoichi wordlessly judging him.
After resting at the Wisteria House due to their injuries, they are summoned by Tanjiro's crow to head to Natagumo Mountain. Inosuke and Tanjiro rushes into the mountain, with Zenitsu lagging behind due to his fear, after seeing a fellow Demon Slayer asking for help. That Demon Slayer was then pulled backwards back into the forest. After witnessing that, Inosuke acts as the vanguard and orders Tanjiro and Zenitsu to follow him. Tanjiro follows Inosuke while Zenitsu stays near the mountain, refusing to enter.
After meeting with an another Demon Slayer who was hiding from the demons, Inosuke and Tanjiro understands the situation present that the Demon Slayers began to kill each other after entering the woods, due to a demon's blood art making them into puppets that can be controlled. After trying their best to not kill the controlled Demon Slayers, Inosuke uses his Breath of the Beast Seventh Style: Spatial Awareness to find the demon known as 'Mother'. Inosuke and Tanjiro manages to hang the controlled Demon Slayers onto the trees to immobilise them, however, the demon controlling them cracked their necks, killing them after they are immobilised. With heavy hearts, they proceed to the demon's location, but was stopped by a headless puppet controlled by the demon.
During the battle with the headless puppet, Inosuke's hastiness gets him injured and almost killed. Thankfully, Tanjiro saves him and encourages Inosuke to fight alongside him. Even though Inosuke was unwilling, thanks to Tanjiro's instructions, he is able to cut the headless puppet diagonally. Inosuke is very competitive with Tanjiro, thinking he can do everything Tanjiro can. Tanjiro defeats the demon known as 'Mother' and Inosuke is severely wounded, though will not admit to it.
Tanjiro tries to get Inosuke to get down the mountain and he refuses. They catch a glimpse of a demon girl, who Tanjiro could not smell due to the putrid scent surrounding the mountains. The demon girl calls for another demon called 'Father', who is a large man with the face of a spider. He is a strong demon, though not a Twelve Demon Moon, and Inosuke is staggering from blood loss. Tanjiro is sent flying away due to the demon's strength and shouts for Inosuke to not die at all costs. Inosuke manages to cut the demon's arm, making him climb up to trees to shed his skin and show an even larger spider-like body. Inosuke tries his best, but his blades broke and he was strangled by the demon. Luckily, Giyuu shows up and kills 'Father', saving Inosuke's life.
Inosuke, despite his wounds, tries to challenge Giyuu but gets tied up. This makes Inosuke's confidence in himself drop and makes him think he is not as good as he thinks he is. Inosuke is then released from the ropes by the Kakushi or 'Hidden' which are the squad that deals with the aftermath of demon battles.