Responses

If I understood, Minjae was dating his ex that was introduced by his friend, his ex and friend were fuck buddies and they continue to do it even when Minjae and ex were going out together. Minjae didn't know their relationship, and that friend told him it was Minjae who came between them (cause he was in love with him??? Bro just confess then...)
Conclusion that ex is a cheater and hurt Minjae :/
Now matter how many times I read it, I can't understand the ex situation (个_个)
Can someone care to explain it to me ?