Profile

Kouzuki Mio is a first-year at Kouhei's school who is unable to speak. In place of her voice, she communicates using a sketchbook she carries around with her.

She meets Kouhei in a rather comedic situation--she trips and spills her udon all over his back and insists that she clean it for him. She's an energetic girl who clings to Kouhei's arm regularly. She also carries around an older, battered sketchbook that Kouhei is annoyed at... Spoilers follow.

Mio had in fact met Kouhei earlier in life, when they were children, and that notebook is the one Kouhei had given her to communicate with. It appears that Kouhei had made a promise to meet Mio again, but he wasn't able to, and Mio ended up putting her entire livelihood on that notebook--to use a phrase from the game, the notebook had become her ball and chain.