Aki Shimizu (清水亜希) is a female tennis player and the reigning champion of the All Japan Junior tournament.
Shimizu has a brown chin-length bob, with long bangs. She has large eyes and is generally referred to as "Aki-chan," hinting at her more childish appearance.
Shimizu is usually shy and quiet. She is also not quite fond of electronics like cell phones, which is unusual to her generation. While she seems to be "emotionless" during tennis matches, her emotions are more obvious when outside matches. She seems not to know how to handle her emotions, thus, she is shown to be blushing more or panics.
Despite her age and shy personality, Shimizu is a very strong player, who had won the All Japan Junior tournament as a freshman. Her technique has no wasted movements, is fast and accurate, and been described by Eiichiro as machine-like. This is due to her mother being her tennis coach ever since she was a child.
Shimizu first met Eiichiro in the All-Japan Junior Indoor Selectionals when Eiichiro picked up her phone battery when she dropped it.  Ever since then she has slowly developed a slight crush on him, as confirmed by Natsu.