This whole manga was pure trash. Honestly, what was even the point of it all? Minoru died 4 years ago, during this time Asahi had NO intention of murdering Wataru at all, she did not care about him at all, if Minoru was so obsessed with protecting Wataru, why did he even interacted with Asahi knowing she's obsessed with him?
"Well he's a evil spirit, so he wants to kill people!" By this logic, he should've also wanted to kill Wataru, because he went after Asahi for no actual reason, since she didn't want to murder Wataru until he gave a reason for her want to.