Suibi Cavern (翠微洞, Suibidou), known also as the Bluemist Aerie, is the personal residence of the hisen Riyou, who is known as Suibi-kun (翠微君, "Lady Suibi") as the mistress of the aerie. It is located on Mount Ha (琶山, Hazan) in the kingdom of Sai.
Suibi Cavern was granted to Riyou by Fu-ou, a previous king of Sai for whom she had been the favoured concubine, as a reward for admonishing him so he did not lose the way. When she was exiled from the court by ministers so she could no longer influence the king, Riyou took up permanent residence at Suibi Cavern. Out of bitterness and boredom, she is very abusive towards her servants, who were eventually all taken into the service of Kouko, the current ruler of Sai.