Yumemi Seiun (星雲 ゆめみ Seiun Yumemi) is an Earth girl and the main character of the Heirloom Star series. She is sought out by Navi to activate her powers from the constellation Lepus, taking the place of the magical girl of the same name.
Yumemi is a tall, stocky girl with tan skin, shoulder-length black hair and hazel eyes. She is frequently seen in country or mori-style lolita fashion, which she usually sews herself. Her hair is almost always styled with one of her bangs done in a braid and decorated with a teal ribbon headband.
Yumemi is a quiet, but kind-hearted girl with a positive attitude and helpful demeanor. She enjoys the consistency of ordinary life, although she admits that she finds it lonely, and dislikes change or anything else unexpected. This partially explains her reluctance to accept Navi's initial offer. She bakes and sews clothes as a hobby, as well as to cope with negative emotions, usually after a fight with her mother. Interestingly, she requires very little sleep and food to keep her body healthy, and her lack of sleep is a source of concern for her friends. She keeps these facts about her a secret, as she feels they wouldn't believe her anyway.
In the novel, Yumemi is first introduced when has a dream about a far-off fantasy world, inhabited by a mysterious woman. The dream leaves a strong impact on Yumemi, even after she wakes up, especially since this is a recurring dream. Reluctantly informing her mother Megumi of her plans, she spends her Saturday morning with her best friend Tomomi and her boyfriend Kenichi at a college campus' duck pond and then at the mall, where she and Tomomi brainstorm methods to make fast money with consumer products, much to Kenichi's beguilement. After trying and failing to find a gift for Tomomi's impending birthday, she manages to acquire a card from an ostenateously hyper young woman running a small shop in the mall and leaves.
The woman is revealed to be Fornax, using her powers to pressure the original store's cashier to not attend work by twisting her fears and discovers that Yumemi has dormant powers belonging to the constellation Lepus. Fornax leads and traps Yumemi into the mall after midnight and attempts to steal her powers by sending her Star Spirits to pursue and apprehend her, but Yumemi is rescued by Lepus herself after she tries to escape from the mall, who she recognizes as the mysterious woman from her dream. Lepus knocks out Fornax and helps Yumemi leave the mall, giving her water with magical properties to heal the ailments she sustained during the encounter. Yumemi tries to make conversation with Lepus, who is mostly unwilling to open up to her, and learns that she is a magical girl who walked away from her former life. She leaves Yumemi, who sneaks home alone, unable to sleep due to fears that torment her from being tricked by Fornax.