Kei is a childhood friend of Sawaki and, like him, a freshman. His parents run a sake brewery (making them customers for the mold starter from Sawaki's parents).
It is revealed after a brief disappearance by Kei from the main plot, that Kei is gender dysphoric, and has stronger feelings for Sawaki than initially let on.

The central protagonist of the series, Hibiki Amawa is a fairly typical optimistic college graduate whose goal is to become a professional school teacher. His life takes an unexpected turn in the process when, in order to pay off his apartment rent, he is forced to cross-dress in order to gain employment at the sexist Seito Sannomiya Private School. His situation only gets more complicated when the school board grows suspicious of him, students begin to clash and one of the girls of his class develops feelings towards him. However in spite of all the unfortunate difficulties he faces on the job, Hibiki is in fact a very competent and focused young man who proves that, man or woman, he is proficiently capable of teaching fitness and counselling.