Ai Zai Xiyuan Qian

This is a group of people abandoned by time, their love misplaced before BC. In the primordial cycle of reincarnation, in the cracks of time, they were destined for a brief reunion and an eternal loss… Ten days, merely an ordinary unit of time, is an insurmountable eternal rift for them! Searching through lifetimes, all they can do is remember each other's marks, waiting for fate to awaken again! A thousand twists and turns, a tragic love—"Love Before BC"

(Source: iQIYI, translated)