Blood. Is Jongin’s weakness—no, he’s not scared of it, never. That’s not the case, he’s too fascinated by blood to the point whereas he would harm himself to catch a glimpse of the crimson red flowing down his smooth skin and he will not stop until he’s satisfied with it. And if you’re thinking Jongin is mentally unstable or somewhere along those lines, you’re wrong. He is perfectly fine, he knows what he’s doing and that’s what scares him the most—of course, the current Jongin wouldn’t know what his weakness was due to memory loss.