The Golden Man
The Golden Man is a story written by Kuruki. It ran in Issue 22 at http://s2b2.livejournal.com/120116.html, and is mirrored at http://www.shousetsubangbang.com/mirror/the-golden-man/.
From the author: "Mercenaries raid Bao's home. Will he be able to save his mother? his sisters? and at what price?"
From delicious.com: "Warning for dub-con The palace is overrun while the khan is away and the prince makes his way to the harem, where he rescues his sisters and hides them. Unfortunately, he is found and the only way to keep the girls safe (and to keep himself from being the victim of a gang bang) is to give himself to the golden man who finds him."