Before Shinjuku, Gojo hatched a plan where somebody would take control of his body in case he dies as a last resort. Yuta lost it on everyone, no one wanted to do it and really no one even cared about Gojo, except a few. Yuta decided that he would become that "Monster" Itadori was the only one left out due to his connection to Sukuna, because Sukuna would hear and know about their plan.