Shoto has 28

Shoto's mother insists on meeting Shoto's partner, but he doesn't have time for dating, so he decides to arrange a marriage with a stranger. He will pay her, and she will pretend to be his wife to keep his mother happy.

What he doesn't know is that his fake wife also works for him as his assistant. He never saw her in person again, except when they got married.

Based on a Chinese story whose name I can't remember.