Also known as: 水池海
Character from Watashi No Hatsukoi Aite Ga Kiss Shiteta.
Sexual partner of Rikunaka Chiki, who is later revealed to be Chitaira Shiho, her half-sister, and roommate of Hoshi Takasora, who has a crush on her.
Umi is subject to sexual abuse and coercion at the hands of Shiho throughout the series, but despite this, falls in love with her. Her feelings are maintained even after she learns of her familial connection to Shiho, with whom she begins living at the end of the story.