I agree with your reasoning behind why Viaan only propositioned Katha and then went through with it. That kind of is the only way it makes sense😊
Viaan might have been clean at office and also as he told Katha he might have just tested the women approaching him by this offer to see if they are interested in money or him. But he would not have gone ahead and slept with someone like that. He made an exception to Katha because he was in awe of her ,she challenged his beliefs in the start when they met. Initially he might have just wanted to test her but then when she said yes , he wanted to see whether she will come there or not as per his own monologues he was just hoping that she would not come. But she came and then I believe he took it as a deal between them. What happened after that he confessed to himself that he fell in his own darkness as she was the hope he was looking for and she turned out to be like others.
As for what happened between them, lol Its hard to say Viaan was not attracted to her and her personality. May be love was not there but we can say that he did admire her.
Anupamaa
