Spoilers
but is he really tho?
He is just trying to move on and start a new relationships and even feeling guilty while doing so.
But she is the one who went through his phone without any consents even though technically they are not in a relationship anymore (plus one who does that is usually the one hiding something in relationships), acts like a yandere right after she said it's okay, and literally committing murder to send a "message". Maybe there is a reason why he wanted to move on.
I haven't been in any relationships, so there might be things that I don't know, but I still feel like this wasn't a healthy relationship from the beginning.
idk, It was hard for me to empathize with her.