Well as much I understand "the first kill" supposed to be MC, but because the first murder didn't happen - aka MC is alive - she couldn't leave the house when she went back nursing ML. In the recent chapter he even thinking that sience he doesn't know what kind of thrill murder going to bring to him, there is nonneed to try kill MC, because he's enjoying himself now with her and a dead person cannot came back to life. The police investigating a case a murde in a park, but that happened when ML was sick, and MC was at his side non stop, so she know he is not the murderer even thought somebody planting evidence there, maye that creepy police officer. And yep he is a psicho.
Also the police officer was able to get in the house 2x ! Without her knowing or maybe even him to some extent
Why do i lowkey feel like he’s a psychopath but he isn’t the murderer