@ohyun i think that they both fell in love for each other when they met on february, right after that the ponytail chick got friendly with him. and by april they were going out, the black haired girl is lamenting that if that day back in february she asked to be friends with him then maybe they would have end up together.
so we basically skipped a whole ass romance manga about a fated meeting and the 2 of them not doing anything concrete and one of them ends up with a 3rd person, we could have had a whole ass 200 manga with this premise...