|Japanese name:||羽山 ミズキ|
Blood type: AB
Height: 156 cm
Weight: 44 kg
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-.
Spoiler!In a tale of melodies, she falls in love with Kuze, who she met as child.