As for what would happen if he couldn't return, Professor Di couldn't speculate; only Yan Junze himself was clear on that.
Because his body had already begun to numb intermittently, and when the condition worsened, even his limbs would start to feel unreal.
It was understood that if he didn't go back to save his past self at a certain point in time, it was very likely that after that specified time had passed, the current him would completely disappear.
In other words, he would still have died in the Underground Space during the "Tricky Silk" mission.
The initial conclusion deeply shocked Yan Junze, but after returning to his dormitory and thinking it over carefully, it seemed that only this could explain the oddities happening to him.
Without the appearance of any strangenesses, his body would go numb, his fingers would turn ethereal, briefly disappearing.