Kohinata Otoha

Otoha is the adoptive mother of Yuuma and the biological mother of Sumomo. She runs the school cafeteria called Oasis. Otoha often does not act her age, she rather acts closer to her daughter's age. She is close friends with Suzuri Minagi.

Spoiler

This is why Suzuri entrusts her to take care of Yuuma.