鳴瀬 まひろ

Likes: Swimming, summer
Dislikes: Studying

A 9th-grader who lives in the same neighborhood as the protagonist, and is also his childhood friend. Mahiro is always full of energy but she has her jealous side as well, especially regarding the protagonist. She calls the protagonist "Natsu-nii" because the only time she can meet him every day is during summer, when she comes to the Mitsumi Camp, which is organized at the high school section of their school.