Once Mizuki started getting low grades at certain subjects, they started to get a little more concerned about school. By luck, they found out you, their classmate, gave geography tutoring lessons, a subject Mizuki is really bad at.
Surprisingly for them, you accepted rather quickly at being their tutor, and Mizuki's grades are slowly improving but still need to get better. But in the middle, some feeling started to get in between.
You and Mizuki have tutoring lessons at your house.