Bro why

Why his age progressed so fine??? Also mad predictable story which I loved. Some authors give no fucking hints and pull out the “oh look at this plot twist that makes sense with only the character keep this information to themselves and revealing it last minute.” The moment I saw his past memories, aka his weird dream, I just knew how this story would go with the idol + how would he be in the mortal world with his bf + his similar name. But I loved how later things revealed that I wasn’t so keen on picking up such as how the bf murdered a bunch of people even though he’s clearly a nice guy, only to find out he never killed anyone and it was the doppelgänger cop. But if that was the case, then why was the doppelgänger cop replaced if there was no dead people before him? Or is there other ways to be deemed a bad person. I’ll ignore that question and just enjoy the story.