I think it is Kartik, cause after Charu fell, the police had arrived and Mr Interesting, Very Interesting (don't like the guy, find him annoying...looks like a sour grape) starts asking if anyone actually saw Charu fall. No one said anything. Only Kartik said that 100% kashish had seen Charu fall.
How is Kartik soooo sure that Kashish saw Charu fell, cause Kashish didn't say that she saw Charu fall, she was crying and pointing towards the ledge. I know kashish did see Charu fall, but how is Kartik soooo confident that Kashish saw everything. He wasn't there at the time, he came with everyone else..... Unless he was already there and saw everything......!!!!!!!!
I mean he could have had a hand in Charu's death and with Kashish seeing Charu fall, he thought to himself that he has a witness that Charu fell herself. End of case. But this isn't the case, now he tried to kill Kashish, cause she desperate to know who the killer is. And why else did Kartik try and pin the blame on Kashish, when he went to the police station, to chat with Mr. Interesting. He's trying to get himself out of the frame.
What do you guys think?