Shimizu Aki is a female tennis player and the reigning champion of the All Japan Junior tournament. 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. Shimizu first met Maruo in the Kanagawa prefectural tournament when Maruo picked up her phone battery when she dropped it. Ever since then, she has slowly developed a slight crush on him. (Source: Baby Steps Wikia)
Yuuki Tajima is a middle school student and a member of the Southern Tennis Club. In his 2nd Year of Middle School. He is also proven to be a very skilled player as he is the top seed in the U-12 divison. He is the best in his age group and had to go the Florida in order to find better opponents. He also has been to the Florida Tennis Academy to study during grade 3 of elementary school, but he became homesick in three days and needed his mother to go over there.
Kishi Teppei is a tennis player in Kanagawa. He is first introduced in a match against Eiichirou Maruo in the third Kanagawa Junior Tennis Circuit where he was the 5th seed. (Source: Baby Steps Wiki)
She is Katsumi Ogata's Girlfriend.
Hana Yokoyama is one of the female players at Southern Tennis Club. She is friends with Natsu and Masumi and is a regular player at the Kantou Tournament. (Source: Baby Steps Wikia)
Azusa Sumiyoshi was one of the top high school players during his high school days. He was seeded 2nd for the All Japan tournament. He reached the semi finals of the same tournament. (Source: Baby Steps Wiki)
Yukichi Fukazawa is a member of Southern Tennis Club and a friend of Eiichirou Maruo. He has knowledge of many recurring tennis players and calls E-Chan, Aniki (Big brother).