Hina Tachibana

She is the elder sister of Rui Tachibana, but soon after Tsukiko Tachibana (Hina's divorced mother) marries a widower named Akihito Fujii, Hina becomes the stepsister of Natsuo Fujii.

It is also pretty much likely that due to a necessity of a paternal figure added to the kindness of Shuu, she developed a crush on him, which led her to get involved into an affair with him time after they ran into each other as she was in her fourth year at the university.
It is not so clear if she feels becoming a teacher is her true call, even though she admits she has worked really hard to get her license. She is really into comedy shows. She does enjoy festivals in general, not only for the food but for the different attractions, especially the goldfish scooping. She is afraid of cockroaches to the point of running away from seeing them, without worrying if she is wearing something or not. She also freezes up with thunder storms.