I was reading a shoujo manga where the protagonist's crush ends up with her older sister. When the protagonist sees them kissing she runs away and somehow ends up going back in time to have a chance to confess before her crush and sister meet each other. The crush's friend seems to have feelings for her and might have been responsible for her going back in time.

Any help would be great >_<. I forgot to save the title.

Heptagon? I read it almost 5 years ago so not certain, though.