羽山 ミズキ

Mizuki goes to an affiliated school and admires Kei greatly as someone who is older than her; in fact, Mizuki is also on her school's girl's basketball team. She greatly enjoys reading shōjo manga. She has a straightforward attitude and likes to be frank towards others, especially to Kei.

She's the main heroine of the fourth chapter from the ''Ef'' series: Ef -The latter tale-.