Eiichiro Maruo (丸尾栄一郎), also called Ei-chan, by his friends is the main protagonist of the manga, Baby Steps. He later becomes a member of Southern Tennis Club on his mother's suggestion to fulfill his lack of exercise. His current aim is to become a professional tennis player.
Eiichiro has an average stature for a tennis player. He has an odd hairstyle with short hair on the sides and spiked hair in the middle. He has a superior eyesight as compared to dsa normal person. After training hard for becoming a professional, he has muscled up a bit and his body has become totally tennis oriented.
He usually wears uniform at the school and tennis clothes at the club. Another noticeable feature is that he always carries a bundle of notes with him, be it for studying or for tennis. After he muscled up, he is considered to be quite handsome, as noted by several females during the series.
Eiichiro has a perfectionist personality and is also called All-A, referring to his perfect grades. He tries to achieve perfection in every task that he performs, be it studies or tennis. He works very hard to achieve his goals to an extent that it even surprises his friends and tennis club members.
He is sometimes referred to as a high-school boy who sounds like an old man due to his habits of trying to do everything in order to be perfect.
During his second week at high school, Eiichirou continues writing his study notes. When E-Chan was eating his lunch, Natsu Takasaki from class 2 appears to borrow his world history notes. After Natsu describes E-Chan as weird (as his notes look excessively perfect), she accidentally falls down and ruins his notes. After school, Kojirou Kageyama invites him to the shougi club, but E-Chan rejects him and explains that he wants to participate in some exercise. Upon arrival at home, his mother persuades him to visit the neighborhood tennis club, Southern Tennis Club. At first he refuses to go, but his mother snaps and forces him to visit.
As he arrives at the Southern Tennis Club (STC), he is amazed by the size and facilities it consists. He notices Natsu Takasaki playing tennis in one of the indoor tennis courts, but is discovered by Kajima Yuuki. Yuuki immediately believes that he is spying on them and yells loudly, hence bring everyone's attention to E-Chan. After being discovered, Nacchan introduces him to the players of the Southern Tennis Club. He reluctantly joins the warm-up exercises which involves running 10 laps, 10 line touches, jump and dashing, 5 sets of side-steps, dashing, and etc. Unfortunately, E-Chan collapses after doing all the exercises and is called pitiful by the elementary school student Yuuki. Afterwards, he finds an excuse to leave, but is questioned by Natsu of whether studying is fun. Natsu reveals her intentions to become a professional tennis player, which causes E-Chan to reflect on his life. When he was riding the bus home, he decides to get off half the journey and run back home. He later collapse again whilst running, and asks his mother to pick him up.
The next day, Natsu passes a message from coach Morimoto, to him. He is invited to the Southern Tennis Club again to practice playing tennis. After a few days, he decides to visit the tennis club again and successfully finishes the warm-up exercises without collapsing. Whilst waiting for coach Morimoto, E-Chan decides to observe A court. He is introduced to Takuma Egawa who demonstrates a powerful serve which intimidates him. After Nacchan teaches him the basic stance to hit the ball, he successfully hits a light serve from Takuma. After his successful hit, he begins to practice playing tennis, even though he is unable to produce the same shot. He also develops a Tennis Edition of his notes, just to feel the great sensation again, from his first successful shot.
Following his hours of practice he discovers Nacchan and Takuma, and believes that they were dating. To his appreciation, he discovers that it was a misunderstanding. Soon after, Nacchan finds him hiding in the bushes and she joins his tennis practice. As she leaves, Kageyama perceives that he likes Nacchan, hence causing E-Chan to feel flustered and confused. At home, he looks up at a dictionary for the definitions of like and love. The following evening, he spends approximately 6 hours practicing tennis. Even when Nacchan calls his name, his concentration prevents his from realizing her. For the first time, Natsu says that E-Chan will become a strong player, but Takuma shows his doubts.