A love relationship should be based on trust. If there is no trust in the relationship, there is no point pursuing such a relationship. Mukti may have trusted the FAB 5 when they revealed that Harshad is having an affair instead of trusting him. So he may have broken up the relationship. However, one can see that he still cares for her and get close to her at every opportunity possible. Harshad was worried when he found Mukti was trying to commit suicide and rushed to save her. He also was concerned about her having anti depressant pills. Even when he is dancing/talking with Navya, if Mukti is in the room, he has eyes only on her. Despite of his Cassanova title, he was not seen sleeping around with anyone. He is close to Navya, but he has not used her in that way.
Mukti, on the other hand, is still not over Harshad. Whenever she sees a happy couple / Navya with Harshad, she takes anti depressant pills. Mukti gets jealous when she sees Harshad with Navya. She sleeps with X, Y and Z and then throws them away like used clothes. Even when she is with another man on bed, she sees only Harshad. When she is dancing with that Hunk on the Diwali Party, she has eyes only on Harshad. She thinks that Harshad is guilty, but still offers to sleep with him so that he leaves Navya. She is also angry that Harshad has not given her an explanation.
So, it is possible that Harshad suffered because of a misunderstanding and wants to take revenge on the FAB 5 for influencing Mukti. What do you think?