Tadanori Yakabe is tennis player ranked 36 in Kanto Junior. Eiichirou Maruo described his playing style to be similar to Alex's. Tadanori is highly skilled player, being one of the highly seeded players in All Japan Tournament. Tadanori was essentially a baseliner specialist with a strong serve and flat forehands. His shots are not exceptional but has a variety and are usually powerful. His serve is not on par with Takuma but is still very fast. He started using Serve and Volley to increase his arsenal of techniques. He uses it in combination with his fast serve to make it effective. He has improved his skills but is relatively inexperienced in Serve and Volley. (Source: Baby Steps Wiki)
Kojirou Kageyama is Eiichirou Maruo's friend at Oosugi High School. He attends most of E-Chan's tennis matches along with Himeko Sasaki. (Source: Baby Steps Wiki)
Kanda Hisashi is a young tennis player from the Kyushu region. He attends the Illustrious Yanase High School and was the 5th seed of the first All Japan Junior Tournament. (Source: Baby Steps Wiki)
Watanabe Ken 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 14th seed. (Source: Baby Steps Wiki)
Eiichirou's father is the one who first accepted Eiichirou Maruo's plan to become a professional tennis player after hearing his proposal. Eiichirou's father has a somewhat mild personality. He was ready to give Eiichirou a chance to become professional in tennis. Later on, he was ready to help E-chan in anything he wants for his tennis training, claiming that until the All Japan tournament, he will provide any help he wants since Ecchirou wants to become one with his own will and is willing to work hard for it. However, since Eiichirou said that he would give up on being a professional tennis player if he did not win the tournament, He plans to make Ecchirou keep that promise.
Eiichirou's mother has a strong personality and has her say in all the family matters. She is proud of her son and wants to help him. She suggested to Eiichirou to go to STC, when he claimed he needed some exercise. But she was against him taking it too seriously and was angry when he told her that he wants to become a professional tennis player. Later on she agrees on a condition that if he loses at All Japan tournament, he will quit. (Source: Baby Steps Wiki)