Theory? Yooyoung cursed MC in their past life, committed suicide probably as a part of the ritual. MC gets hit by the curse (maybe Yooyoung made it so MC would die if he died?) and dies (what happens in the dreams). Yooyoung cursed MC so that anyone who gets close to MC would die, including his family because Yooyoung is insane. That’s why only Yooyoung can be close to him without dying, and why Yooyoung can stop those nightmares etc. Yooyoung made it so that MC would have to rely on him for everything and be unable to get close to anyone else except him.
Theory?
Yooyoung cursed MC in their past life, committed suicide probably as a part of the ritual. MC gets hit by the curse (maybe Yooyoung made it so MC would die if he died?) and dies (what happens in the dreams). Yooyoung cursed MC so that anyone who gets close to MC would die, including his family because Yooyoung is insane. That’s why only Yooyoung can be close to him without dying, and why Yooyoung can stop those nightmares etc. Yooyoung made it so that MC would have to rely on him for everything and be unable to get close to anyone else except him.