Megumi Nakajou is a very skilled tennis player. She won the All-Japan in middle school and is a freshman high schooler. Megumi is very skilled and was able to trouble Natsu by not letting her settle down. She is said to have a somewhat odd style of tennis.

(Source: Baby Steps Wikia)

Eiichiro Maruo is a straight-A student who decides to take up tennis as a side hobby upon entering high school. At the tennis school he runs into Natsu—a bit airheaded, but nobody can beat her in passion for the sport. Soon Eiichiro gets addicted to tennis...and when he applies his academic skills to improving his game, the results will change his life forever!
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(Source: K-Manga)

Based on the original manga by Hikaru Katsuki, Baby Steps centers on a honor student named Eiichiro Maruo who becomes frustrated with his life and decides to join the tennis club. Despite lacking experience and physical strength, he utilizes his studious nature to develop a strategic approach to playing tennis. Taking notes of his opponents’ habits and tendencies, he is able to predict their next move before they even react. He also meets Natsu Takasaki, a beautiful girl with a passion for tennis. With her help, he aims to become a professional tennis player.
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(Source: Crunchyroll)