On the 7th, when Mingtai was hallucinating, there were countless shots in his mind. He thought he was going to die, and countless beautiful pictures flashed through his mind. The first photo is his wedding photo with Yu Manli. Then mom, Jinyun, and the big sister family. Please note that the photo with Mary is not just a meeting, not a task, not coming back to see each other.
This shows that in Ming Tai's subconscious, he loves Yu Manli and wants to marry her, but what he wants, what he wants to marry, is a white wedding dress, pure Yu Manli, not Yu Manli who is unbearable in real life. He tried so hard to suppress his feelings for Mary that he thought he didn't love her. Only when he is hallucinating, the subconscious mind won't lie.
There are details repeatedly confirmed by Wang Tianfeng in the play, reminding Mingtai not to fall in love with Yu Manli. Who is Wang Tianfeng? Why did you remind him repeatedly? Of course he knew that Mingtai liked her and would die for her. He knows better that Master Ming can't accept Yu Manli's life. Yu Manli's death is inevitable, and so is his death for Ming Tai.
Even if she didn't die this time, as long as the future task is in danger, she will be desperate to die for Ming Tai. This is her fate, otherwise how will their story end?