Introduction to the Tennis World Arc is the first arc in the series which features Eiichiro's first encounter to the tennis world and his first tennis tournament. It lasted for 16 chapters and 7 episodes.
Eiichiro Maruo, also known as E-chan, is in his high school class, a girl from another class called Natsu Takasaki arrives to meet her friend Yuki. She asks for her history notes, but is given E-chan's version, claiming they are better option. After seeing E-chan's notes, she claims that more than amazing, they are weird. After E-chan gives her his original notes, she ends up falling at the door and spilling lunch on it. She roughly cleans the notes and apologizes to E-chan for getting it dirty, smiling cutely and mesmerizing all the boys.
Later on their way back home, Kageyama asks him if he joined any clubs. Kageyama invites him to Shogi club, but E-chan claims he needs to do some physical exercise showing him his busy schedule. Kageyama asks him if he really enjoys studying , but E-chan doesn't understand what he means. Eiichirou decieded to visit the Southern Tennis Club.
There he sees Natsu playing and is surprised by her skill level. While he watching, Natsu arrives and recongnizes E-chan and introduces him to everyone. The coach asks him to stay there and have a look. Soon the warm-up starts and everyone enters a serious mode. Eiichirou gets along and starts exercising but cannot keep up till the end and collapses. After waking up, he tries to leaves but bumps into Natsu. When Eiichirou tells her that he has to study, she asks him if he really has fun studying, to which he has no answer. He guesses that she is playing tennis for fun, but is shocked when she tells him that she wants to become a tennis pro.