Masamune-kun's Revenge R

Eight years ago, Makabe Masamune, a weak and chubby boy, was harshly rejected by the beautiful Adagaki Aki. Now, he's lost a ton of weight, changed his name, and returned as a handsome teenage boy...

all to make the "Brutal Princess" Aki fall in love with him so that he can reject her just as harshly as she did.