Qin Shi Ming Yue: Tian Xing Jiu Ge  

Qin's Moon: Nine Songs of the Moving Heavens, The Legend of Qin: Nine Songs of the Sky, 秦时明月 姐妹篇：天行九歌, Qin Shiming Yue Zhi: Tian Xing Jiu Ge, 秦时明月天行九歌, Qins Moon: Nine Songs of the Moving Heavens

The Qin State poses a threat to the Han State, which is known as the weakest among the Seven States. However, unbeknownst to the Han Emperor, the real danger lies within the Han State itself - the Great General of Han, Ji Wuye. He leads four powerful warriors in military, finance, politics, and espionage, collectively known as the Four Fearful Warriors of Nightfall. Han Fei, the ninth prince of the Han, formed Quicksand with Wei Zhuang, Zhang Liang, Zinü, and Nong Yu in an attempt to establish a new Han State. However, their ambitions drew them into a vortex of power called "world," which threatened to consume them entirely.

Nine Songs of the Moving Heavens is the prequel to Qins Moon (The Legend of Qin). Although the two animations have intersections of characters and their timelines, Nine Songs of the Moving Heavens is an independent story.(Source: edited from wikipedia)