I think Yang Luotian might be considered the first transgender lead in a Chinese drama?

Merperson Yang Luotian has always gone as a boy for most of his life. That is, until he saved Lie Hengyu from drowning. When a merperson first falls in love, the equivalent of puberty hits and their body begins to take on one gender. Yang Luotian finds his body and mind slowly turning female.

To avoid scrutiny over her sudden changes, she switches colleges, only to still pose as a man after being recognized by her childhood friend. She soon ends up roommates with Lie Hengyu. As if it’s not hard enough hiding her gender from him, she also has to hide the fact that she cries pearls and her scales flare up when her skin touches water.

The Rules of Love 人鱼恋爱法则 uses mermaid magic to put a new twist on the classic troupe of “woman crossdressing as a man but falls in love with her roommate” troupe that’s been popular in China since at least The Butterfly Lovers. The series will be released in two parts, with the first 12 episodes came out yesterday and the second 12 episodes on April 4. Watch it on iQiyi here.  Directed by Huang Tien-Jen (Attention, Love! ), the series stars newbies Wang Yanbin, Li Junyao, Fan Xiaodong, Shi Xueqing, Hao Mingqi, and Yuan Liruoxin.