The two main characters are exes. The protagonist broke up with his long-term boyfriend and later on met his ex's younger self from about 10 years ago, I think? This younger version of his ex obviously doesn't know about the break up, making the protagonist feel guilty. Eventually, that guy is replaced by another version, this time from 5 years ago (might also be wrong). Turns out, the present version of the protagonist's ex somehow switched with these younger versions of himself and also met the younger version of the protagonist from the timelines he entered. They get back together in the end after meeting as their current selves.

Other details: the ex's nickname is Candy. I think they had English names, and the art wasn't in the typical anime/manga art style.

pls help TT

Sounds like This Ending

http://i.imgur.com/LxhWm.jpg (will reformat this some day…)

thank u so much!!! that's exactly what i was looking for 😀D