citrus (Original Japanese Version)

Aihara Yuzu, an innocent high school girl, transfers into a prestigious girl's academy after her mother remarries. On her first day she sees student council president Aihara Mei kiss her teacher! And at home, Yuzu learns that Mei is her new step sister?!

During their first night sharing a room, Yuzu had her first kiss stolen by her step sister! Afterward Yuzu can't get Mei off her mind, but Mei herself goes on as if nothing happened.

Yuzu realizes the truth about her feelings for Mei. Wanting to follow her emotions, Yuzu visits the chairman's office to try and reclaim her relationship with Mei after she went away.

After confronting Mei with her feelings and kissing her in the chairman's office Yuzu agonizes over not being able to face Mei. Meanwhile, the student council vice president Momokino Himeko becomes suspicious of what happened in the chairman's office.

After Himeko claims to have crossed a line with Mei, Yuzu gets competitive and wants to cross that line too. At school, both compete to see who will eat lunch with Mei, but Mei turns them down and leaves them equally crestfallen.

Mei's father, Aihara Shou suddenly returns home. While Yuzu is surprised to meet him for the first time, she explains to Shou how hard Mei's been working for the academy.

Mei and Yuzu study together so Yuzu can place well enough on their exams to keep their grandfather happy. However, after their kiss of mutual yearning, Yuzu can't concentrate at all, and asks Mei what that kiss meant.

After accepting Matsuri's forceful invitation to hang out after school, Yuzu takes Mei with her to meet Matsuri. Matsuri greets Mei with a cold stare, having believed she'd meet Yuzu alone, and then proceeds to drag Yozu around the shopping mall.

With her dislike of Yuzu and Mei's relationship, Matsuri uses the secret photo she took at the shopping mall to blackmail Mei. Meanwhile, Yuzu struggles to bake a cake for her first Christmas together with Mei.

While Mei was able to express her feelings on Christmas, Yuzu couldn't respond sincerely and their relationship grows more awkward. Later, Yuzu oversleeps and misses the train for the school trip, but runs into a pretty girl who also missed her train.

After Yuzu reunites with her class, she tries to talk to Mei about what happened on Christmas. However Mei tells her to forget about that night. Tachibana Nina witnesses their exchange, and resolves to help fulfill her sister's destiny.

Yuzu promises Nina that she'll support Sara, but she can't help but feel shaken after learning that the girl of Sara's dreams is Mei. Nina ignores all the attention she's drawing, desperately holding Yuzu back to keep her from going to Mei.