Myon

Nishi's childhood sweet-heart who has recently become engaged. Myon and Nishi lost track of one another as they grew older. Myon appears to be aware of Nishi's crush on her when they are reunited, but is disappointed by Nishi's lack of confidence. Myon works at her father's yakitori restaurant with her sister. She was a swimming champion during high school, but eventually she grew up when her breasts became too big, as a consequence she could not carry on with that activity and gave up.

(from Wikipedia)