AH, IT'S here.
Yuno didn't want to say this, but there was a story behind his ability to touch the insides of his chest without dying.
Ironically, he tried to harvest his own Core before with the intention of dying.
But he didn't try to kill himself because he was tired of living— he did that out of spite since 'Father' kept asking him to practice harvesting the Cores of dead Guides he would occasionally bring to him.
Yeah, I could die out of spite.
Of course, Yuno couldn't be as petty as he was when he was younger.
A certain Esper would destroy the world if I died.
"Gayoon Hyung, please don't make that face," Yuno said, smiling at Ki Gayoon to assure him that he was fine. Of course, he wasn't just sure if he looked alright at the moment. "I already have the Esper Core in my hand."
Ki Gayoon frowned, and then he sighed— avoiding Yuno's gaze. "Lee Sarang."