We see that Raghav threatened Mahir against marrying Pihu to make sure Pihu doesn’t get engaged to him. Mahir believes this and falls for Raghav’s trap.
We see that Raghav goes out of his way to not let Pihu get married to Mahir. He threatens Mahir, claiming that he loves Pihu and will kill Mahir if he tried to get closer to Pihu.