We all are curious as to where he took kaajjal and why he took Kaajjal. i watched the last episode again and found out the answer.
Dhruv thought that, Dev tried to seduce her in a hotel room,he had hurt her still she chose him that means if I go to do the same i.e lock her up in a hotel room then she might be ready to marry me😃😃
The same hotel room theory by Dev😛