Bird of Youth

From Evil Flowers:

Qing Chun, a canary, and Chen Di, a rooster, are demon birds that can transform into humans. Chen Di is responsible for waking humans up every morning with his singing, while Qing Chun is in charge of easing everyone’s hearts with her beautiful songs. Qing Chun falls in love with Pan Yi, a human, and just once, she would like to be the one who wakes him up in the morning. This leads her to ask Chen Di for permission to replace him in his duty for a day, and in the end, he agrees because he loves her. However, things don’t go exactly as planned for Qing Chun, and Pan Yi somehow ends up discovering her secret.