Ariv’s way of looking at Tanu

I saw yesterdays episode when Tanu calls Vikas and tells him that Ariv is in her room When Ariv is about to leave after giving an explanation on what he is doing in Tanu's room i noticed the way Ariv was looking at Tanu in full concentration as if obsessed. Can anyone tell me why is Ariv after her and when did he fall for her???