OVA
Description
Kaen is a character who appears in the first OVA of Fushigi Yugi, bearing a striking physical resemblance to Taiitsukun in her true form as the Jade Empress. Her appearance is notable for her tan skin, pale brownish-orange hair styled similarly to the character Kashimaro Miiru, and her blue-black eyes. She is depicted as a gentle and kind individual who speaks sparingly, yet this demeanor masks a more deceptive nature, as she is also the one who administers the poison known as Kudoku to Tamahome.

Within the story, Kaen emerges at a moment of profound crisis for Tamahome. After being repelled by the barrier of Suzaku from the Konan palace, he is confused and horrified to discover that the ogre symbol on his forehead has been replaced by the heart constellation, the mark of his enemy Nakago. It is Kaen who approaches him, addressing him as Nakago. She explains a startling scenario: when Tamahome defeated Nakago, the Seiryuu warrior did not truly die but instead fell into a deep sleep. Upon reviving, Nakago’s soul took over Tamahome’s body, while Tamahome’s own soul was displaced into Nakago’s original body. To help him accept this reality, she offers him a bowl of sake to calm his nerves. After Tamahome drinks the sake and falls asleep, Kaen removes her clothing and offers to use Soi’s ability to raise his ki through a union. However, it is later revealed by Tenkou that the entire experience, including her interactions with Tamahome, was merely an illusion created by the Seiryuu seishi Tomo, though the Kudoku poison that Tamahome swallowed with the sake was real.

The name Kaen also carries significant weight outside the OVA, as it is the original identity of the Seiryuu seishi Soi as depicted in the side story novel Seiran den. Born into poverty, Kaen was sold to a brothel by her family at the age of ten and was forced into service. She was known there as Haku Kaen, and proved to be ill-suited for her maid duties, often tripping or spilling things. At the age of twelve, she was ordered to begin taking on customers, a fate she desperately tried to avoid. Her first attempt ended with her slapping a customer and fleeing, only to be caught and saved by a Kutou soldier she would later learn was Nakago. She was eventually freed from the brothel by another soldier named Eichuu, who was in love with her, and she went to work in the palace as a servant girl. In the palace, she encountered Nakago again and her feelings for him deepened, much to the jealousy of Eichuu and the observation of Tomo. It was after a confrontation with Eichuu that her power awakened, and she discovered the character fusa glowing on her thigh, realizing she was the Seiryuu seishi Soi. Her ability, known as bouchuu magic, allowed her to raise a partner's ki through intimate coupling, and she offered this power to Nakago, even as she recognized that his heart was closed off and he kept others at a distance.