Tachibana has light-coloured wavy hair tied in a loose ponytail. She was also seen wearing a clip. Her eyes are dark-coloured and she usually wears the school standard female uniform.
Mei claimed whenever it came to nonexistent students like herself and Kouichi, Tachibana wasn't sure how to respond, often becoming terrified. Unlike most senpai, Tachibana refused to give Mei advice.
She made her debut in chapter 11 as a art club-senpai and an ex 9th Grade Class 3 student. When Mei first asks about "non-existence" and co. , she became terrified and didn't give Mei any advices. When Mei asks again carefully, she said that she can't recall anything about Asakura Mami, the 1996 extra one. When Mei aks about the "non-existence" student, she tells that his name was Sakuma-kun and that after semester 2, because of the pressure and rejection, he broke the agreement. After the new year started, he commited suicide.
- Her surname, Tachibana, means " Erected Flower."
- Senpai is a suffix of respect for ones' elders; roughly the equivalent of "upperclassman," it refers to students who are at least a grade ahead of the speaker, and is a term of respect, similar to "sensei."