i haven’t read the novel but following the logic of the story, i think the effect is temporary. it wouldn’t have made sense how broken his skill is if the effect it gave was permanent, that would technically be a cheat skill so ig it’s just temporary, he defo thought if yoojin were weaken for a slight duration, he’d be traumatised enough to believe he’s weak even if his stats go back up later on
Actually yes you're right, but the effect is actually bigger to Yoojin.
A little bit spoiler, Yoojin isn't only not being able to stay close with S classes, he's also mentally tortured because the decrease of his fear level made him dreaming about the Yoohyun's death everytime, to the point he finally asked Yoohyun if they can sleep together, and that's how he finally get rid of the nightmare.
Did someone read the novel? What happens to Yoojin resistance skill then? Does it stay C-Class from now on?
Poor Yoojin, he has so much to do. It was already hard with L-Class resistance skill, and now he only has C-Class Σ(っ°Д °;)っ