I've read more toxic than this.
Basically the top is a bit mentally unstable, with his own issues and doesn't realize that what he is feeling is love. That makes him say and do manipulative things and say a lot of mean things to the mc. Some of the things can be considered phycotic such as manipulating him not to leave.
But maybe it's just the fact that I've read way to many shitty toxic stories, so this one isn't even near the top of super duper toxic.
The mc is also traumatized from his previous relationship that leads him to become a bit of a pushover (that's why he doesn't leave). You can say this is a bit of a wrong time in their life for them to be together. Since they both have issues they have to work through. (Some worse than others)
How toxic is the story? I can't figure it out by just reading the comments, spoilers would be appreciated (๑•ㅂ•)و✧