Ozato Fumika

Riku's homeroom teacher. An old friend of the family, she's known him ever since her days as a student.
She's calm and friendly, making her very well-liked among her students.

As Riku's teacher, she's careful to maintain a modicum of professionalism around him, but she still sometimes gives him special treatment.

Her behavior changes completely outside of the classroom, where she acts less like a full-grown adult and more like a spoiled kid.

Translated from the official website