Responses
I think the monster gave Jarn half his heart to turn back time. So Jarn is sort of half monster, he’s made out of the monster’s heart.
Personal theory, time didn’t exactly turn back, they froze in time, so Duke and dog-like-politician, remember real world suffering. So they want to kill monster to unfreeze time, or something similar.

Im really confused what's happening in the story Σ(っ°Д °;)っ