Escape_to_Manga

I read this manga years ago so I don't remember it really well. So this city girl ends up going to a small town school and since she came from the city she becomes popular really fast. The popular guy from the school goes out with her and he turns out to be a jerk. There is this other guy from the school who helps her out and I think she ends up dumping the popular guy. I think later the three of them start having an argument on the roof and the jerk popular guy falls off the roof and dies. I think the guy and the girl decide to run away from the town after that. I never got to finish the ending so I would appreciate it if you know which manga this is.

Does anyone know of any mangas where their are characters that wear a gas mask or a face mask. I have read:
Tenkuu Shinpan
Fisheye Placebo
Tokyo Ghoul

Thanks!