|Chemistry Teacher/ Homeroom teacher (of 3-1)|
Reiko has brown shoulder length hair, either in a small ponytail or loose. She is almost always wearing a white lab coat.
Described as "kind, but strict", she is gentle and caring around her students and the other teachers. She can also be a little lenient with her students, accepting Miyamura's explanation of his pierced ears without putting up much resistance. However, when dealing with Yasuda, her personality completely changes, and she is hostile towards him. She is single.
Terajima is openly hostile towards Yasuda, due to Yasuda's infatuation with high school girls. This stems from her desire to protect her students from him. Often calling him a lolicon or pervert, she is also overly critical of him, yelling at Yasuda for anything she can. In addition, she also sometimes will check on Yasuda, just to make sure he isn't harassing any students or anything. While she knows that Yasuda's targets are usually girls, she is also just as protective of the guys, once checking in on Yasuda's supplemental lessons 3 separate times to make sure he was doing his job properly, even though all the students there were guys. She has expressed her hope that Yasuda quits being a teacher on multiple occasions. Some characters have noted that Terajima's fixation on Yasuda might be due to romantic feelings, but both Terajima and Yasuda deny this.
In contrast to Yasuda, Terajima is her usual self when dealing with Nakamine. This is often highlighted since Nakamine and Yasuda are often together. Sometimes, she will yell and criticize Yasuda for one thing, and be completely fine with Nakamine doing the exact same thing. However, she does kindly note that Nakamine should be more careful about where he puts his things.