Citrus

Despite her gyaru looks, Aihara Yuzu is an innocent high school girl with no experience and no prior loves. When her mother remarries, she's transferred into the prestigious "Aihara Academy" for young ladies. However, on her first day at school she happens to witness the diligent student council president, Aihara Mei, making out with her hot homeroom teacher... Yuzu returns home, unable to hid how upset it left her, when her mother announces Mei will be her new step sister, and they'll be sharing a room...?!

After confronting Mei with her feelings and kissing her in the chairman's office Yuzu isn't able to face Mei and agonizes over it. Meanwhile, the student council vice president who's also Mei's childhood friend, Momokino Himeko, becomes suspicious of what happened in the chairman's office and meets with Yuzu on their day off to discuss it. There she tells Yuzu, "She's incredibly sad. As sad as she was when the current chairman, her father, left her," leaving her in shock. Yuzu's weakly walking to the station home when Mei appears before her...