Aarav - this guy got it all so wrong in the end. There is no questions that he took advantage. But his decisions to hide his part in the mess has led to his embarrassment on national tv.
This is what I think may have happened. It is just a guess from all we have seen.
1. Oviya comes in and has a crush on aarav. First week. The guy is flattered and it appeals to him to flirt back.
2. Second week - every one is trying to find their place in the house. Flirting continues albeit a little more than first week. The tasks add to the allure.
3. The house starts ganging up and oviya is always standing against the tide. Aarav feels threatened about getting nominated if he is seen close to her. So he continues his interactions but lessens it. He starts backbiting about her.
4. I think this is the first trigger for oviya. Her crush has grown to be a little bit more. But aarav is maintaining a distance. She is more attracted than ever. That is her nature to go behind the not possible.
5. I think her "there is no love. Let's just be friends" was a way to get closer to aarav again.
6. Aarav liked the no strings attached kind of relationship. They called it friendship but it was certainly more than that.
7. I think aarav mistook oviya's independent nature to mean that she was ok with love and flirting with some physical contact without the commitment. To oviya these were all first steps to the real thing.
8. The julie week came and went. Aarav probably felt sorry for oviya but even then did not have the guts to call out julie openly. He helped oviya which only made her think this is forever more.
9. Aarav got nominated and he understood that oviya had support. Now his relationship with her was of greater use. I don't believe he did not lead her on. There is one specific conversation that I remember this week when oviya explained to aarav about her dream man. Aarav started that conversation and he said he was trying to understand what she was telling him from their conversation from before. It is obvious that unlike what he told ganesh, he did have some intimate conversations with her.
10. I am me led to believe this as this was the week Vyyapuri kept teasing them about marriage. This was the week even shaktI felt aarav is leading her without being sincere and oviya would end up hurt.
11. I think this week also is the start of the end of their relationship.
12. By weekend, oviya probably confessed that she needed more than 'friendship' and aarav did not. Oviya says no to the shanmugi task because she cannot pretend that her feelings are not there.aarav should have broken it off here. He should have walked away and like Vyyapuri said, should have avoided all the women. He did the opposite.
Oviya's escalation:
13. Aarav is saved from elimination and he sees a way out. If he aligned back to the gang, they would help him out of the mess.
14. He starts to avoid oviya. She grows desperate slowly.
15. He stays with the other women and is rude to oviya. She gets jealous.
16. Then the task is added and it creates more confusion in her head. What is the task and what is real?
17. After going actually bonkers on the first day oviya decides to play the task as by this time she has convinced herself that aarav is only doing the task by avoiding her. She goes total crazy but is laughing as it is her task.
18. Aarav us serious to stay away from her. He knows he messed up 2 weeks back and gave her few promises he had no intention of keeping. He wants to keep her away and uses her act to justify his fear. He takes gayathri, julie and Raiza's help. Plays good and bad cop, badmouthing oviya and praising ger at the same time (she is spoiling my reputation and then she is a nice girl routine )
19. The girls believe him and they have their own axe to grind against oviya. They push her over the edge. He is praising her so he is a good guy. Oviya is torturing him(see what a victim he is. He is still talking nice about her)
20. Vyyapuri and snehan recognize what happened, Vyyapuri due to his experience and snehan because he was there all the time when the above happened. He was both aarav and oviya's confidente. He even seems to have helped aarav at times with advice.
Aarav got caught because unfortunately for him, oviya did not give up. He was ok to have a 'fling' with no commitment but does not have the guts to say it aloud. Oviya was braver though her priorities were different than aarav's.