Have you heard of the mermaids story? 

EXO, the korean-chinese boy group, stucked with a long lost mermaid, Naehyun. One of EXO's member, Chen, had a girlfriend named Daeri. Daeri is the daughter of the CARVE Industries' CEO. Daeri turn angry after Naehyun and Chen's hugging photos were posted on SNS and went viral among all of the EXO-L fansite. EXO planned to teach Naehyun to be EXO's maids but Naehyun traded her voice for her legs and she cannot talk.

 All of EXO's member espeacially Sehun were happy to welcome Naehyun to their dorm except Chen. Chen blames Naehyun for his break-up with Daeri. But Naehyun had a dark secret that makes she never forget about her father's death. Will Chen knows Naehyun secret?

If you want to know the secret, read 그녀의 가장 천사 목소리 (Her Most Angelic Voice)