The Years I Refused to Be a Simp in Quick Transmigration

Crying While Looking for a Book: Quick Transmigration BG, Where the Female Lead Returns to a Small World to Find the Fragments

The first time the female lead enters a world, she falls in love with the male lead, and they live together in a rented apartment. He's a musical genius. His late younger sister dreamed of performing onstage, so he dresses as a woman and enters a competition in her place. The female lead supports him the whole time, but it seems that once the mission is complete, he suddenly leaves without a word...