The Emperor's Last Concubine
The Emperor's Last Concubine is a story written by Yamanashi Moe. It ran in Issue 17 at http://s2b2.livejournal.com/97774.html, and is mirrored at http://www.shousetsubangbang.com/mirror/the-emperors-last-concubine/.
From the author: "For two years, Yanzi has been Red Lotus Blossom, the Noble Imperial Consort. But soon he must return to his old life."
From delicious.com: "Yanzi loves Ying, but when he met he was unaware that Ying is actually the Emperor. When their relationship turns Yanzi into a concubine and puts unexpected pressure on him, Ying gets guilty and decides maybe it was a bad idea. Communication at its worst!"
- delicious.com: "Misunderstandings and angst in a Chinese palace."
- http://biblio-therapy.com/2015/01/10/not-actually-fanfiction/: "This story has the standard Cinderella structure but focuses on what happens after the handsome prince whisks his beloved away and the difficulties faced by both prince and beloved as they both become aware of the golden cage the palace makes."