The imagined CPs are the Emperor Jade and Fat-headed Fish CPs
Runyu x Yunxi (Emperor of Heaven x Ancestor of the Dragon Fish Tribe)
Yunxi is an ancient aristocratic Yu Zaizai. His maternal grandfather is Feng Yi, the uncle of the Yellow River, and his maternal grandmother is Concubine Mi of Luo Shen (the daughter of Fuxi). However, the era of Fuxi has passed, and now is the era when the Yellow Emperor and the Yan Emperor compete for the Central Plains. The mythical beast Bai Ze (later the Nightmare Beast) predicts that Yunxi will have the status of an emperor and empress. Yunxi's mother is worried that other people will know about this, and then casts a spell to send him to a safe place. As a result, something went wrong and he was sent to the era where Runyu is in the future.
In short, it is the story of the love between Runyu and his ancestor