Kobayashi-sensei serves as a mathematics instructor and homeroom teacher for junior class 3 at Narimori Girls’ High School. He shares the faculty room with Hoshi-sensei at the adjacent desk, and their professional rapport extends into a personal friendship, often spending time together at social gatherings after work.

He displays a distinct talent for creative endeavors, once crafting a skillfully made commemorative gift commissioned by parents. On a separate occasion, he joined Hoshi-sensei in reviewing a student’s manga manuscript, and the two collaborated in critiquing both the story and artwork.

His interactions typically reflect professional camaraderie with fellow teachers and conventional teacher-student relations. He frequently appears in mild comedic scenarios set within the school’s daily environment.