Things went wrong, things changed, events that were out of control for the both of you.
I don't know the details myself and can only make well-educated guesses to what actually happened, but what I can tell you is that despite everything-
Bustar still cares for you one way or another and those that you don't recognize, such as Sammy, also care for you and are heartbroken about what is going on with you at the moment.
But still, there's a world of difference between Bustar's care for you and your friends'.
Your friends know what you did and still care for you and have been trying to make you see your mistakes so you can change for the better in your own pace.
Bustar forced that change on you because he can't come to terms with his own mistakes, because the mere memory of hurting you is eating away at him like a parasite. He erased your memories in hopes of erasing the past with it. But that's not the way to do it.
I can't convince him to reverse it, I already tried.
But he may listen to you, if that's what you want.
Sure, you will remember all the bad you did, but you will remember all the good that followed too.
I hate my school years because of the terrible classmates I had and in 7th grade I wanted to jump off a bridge, but that doesn't mean I want to forget my friend who shared my pain and invited me for lunch right after. I don't want to forget all the times I joked and laughed with my best friends during recess.
Yeah, school sucked but I still made good memories that I love to remember!
To be fair, my trauma likely doesn't compare to yours, but I highly doubt there's only hurt.
But in the end, it's your call. Feel free to let it all simmer down first before deciding.