Kamal sir didn't ask Virat to marry Sai he only requested him to take her responsibility. Villagers were adamant about SaiRat marriage. Virat even though initially hesitated has accepted the proposal and married Sai despite her being against this wedding.
After watching today's episode everyone will know why Virat didn't back out and went ahead to marry Sai. His family especially Bhavani would never let an XYZ into the house. Also Ninad, Bhavani kept on saying that they would have arranged some alternative for Sai to live had he told them all this beforehand. Even Virat's statement about Kamal sir saving his life sacrificing his couldn't save the situation so its very clear that he knows very well about his family and their reactions and thought of the only way he could keep Sai with him and take care of her. He married Sai because he knows even if there is a strong disapproval from the family members the marriage bond cannot be overlooked. Somehow Sai has to live with him because she's his wife now.
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