based on day6' days gone by.   

it has been a year since their break up. 

while the boyfriend loved the girl very deeply, the girlfriend no longer felt any sparks between them after a year and a half of dating, and is the one who asked to break the relationship.

the boyfriend still misses the girl, but knows that there's not a chance of them getting back together, and he has no regrets because he loved her with all his might.

the boyfriend may or may not forget the feelings he had for the girl by finding someone better on the show, and the girlfriend may or may not felt regret after joining the show, by seeing the boyfriend with another girl.

based on btob' i'll be your man.

it has been eight months since their break up. dated for a year, they broke things off because of the boyfriend's mistake, so the boyfriend is still in denial and still very much in love with the girlfriend. but the girlfriend is now trying to find someone else because she doesn't want to feel the same pain she felt when they broke up.

the only reason the boyfriend agreed to join the show is because he's trying to win her back.   

based on ikon's airplane. 

both were so in love when they decided to part ways after the boyfriend have to move overseas. they dated for a year, and it has been four years since their break up.