Jujutsu Kaisen S1 eps 10 : 'Idle Transfiguration'  
     
Mahito teaches his ideology to Junpei: as a cursed spirit capable of changing the very shape of a person's soul, he sees people as disposable. Junpei, happy at being told he can kill without feeling guilty about it, has a confrontation with his teacher, who had turned a blind eye to Junpei's bullies. He is about to kill his teacher when Yuji interrupts. Nanami confronts Mahito in the sewers, and during their battle, he realizes that the transfigured humans Mahito makes are actually still alive, self-aware, and in suffering. Nanami's work hours hit overtime, and he begins to use his full power to fight, surprising Mahito.

Jujutsu Kaisen S1 eps 11 : 'Narrow-minded'  
     
Nanami easily emerges victorious against Mahito, but he is able to survive by manipulating his own soul to change his form. Yuji bonds with Junpei over a shared love of movies. Over dinner with Junpei's mother, Yuji tells Junpei that he doesn't want to kill because he feels it would make him value human lives and relationships less. Junpei's mother is killed overnight when one of Sukuna's fingers, planted by Mahito, attracts cursed spirits. Mahito convinces Junpei that one of his school bullies, Shota Ito, did this, planning to lure in Yuji so they can get Sukuna on their side. Yuji arrives at Junpei's school just before Junpei can kill Ito.