Yui Oikawa is Akira's friend that she met from a regular middle school.
When the S.A is punished by the director of the school as a result of Tadashi crashing into the green house and breaking the glass with his motorcicle,they are forced to attend a regular high school for three days where Akira meets Yui, a girl who resembles her childhood friend Sayo. Initially wary, Akira avoids contact with her, but eventually apologizes and befriends her.
However, Akira's fear that Yahiro would break up her newfound friendship results in Akira using extreme measures to protect Yui, who begins to feel awkward around her friends.
When Yahiro investigates her for Akira's sake, he discovers that Yui stole some of Akira's jewellery and threatens her so that she will stay away from Akira. Though Yui had done so reluctantly because her family had financial issues that were forcing them to move, she agrees to Yahiro's demand, but she feels that she needs to say goodbye to Akira and almost gets hit by a car in the process. Yahiro saves her and they end up in Yahiro's home, where Akira finds them. When Akira believes that Yahiro has hurt Yui, Yui clarifies that Yahiro saved her and apologizes to Akira for stealing her jewellery. Happy that they are still friends, Akira ends up helping Yui's family and they keep in touch.