Twelve-year-old tennis prodigy Ryoma Echizen returns from America to Japan at the request of his father, the legendary former player Nanjiroh Echizen. He enrolls at Seishun Academy, a private school in Tokyo renowned for its dominant middle school tennis club, known as Seigaku. Determined and confident to the point of arrogance, the young first-year student sets his sights on securing a spot on the team's roster of regulars.

Upon arriving at Seigaku's tennis courts, Ryoma immediately clashes with the upperclassmen, including Kaoru Kaidoh, a second-year regular known as the Viper for his powerful Snake Shot. Ryoma surprises everyone by copying the shot himself, revealing his extraordinary talent. His actions draw the attention of the team's key members: vice-captain Shuichiro Oishi and his acrobatic doubles partner Eiji Kikumaru, the tactical genius Shusuke Fuji, data-collector Sadaharu Inui, power hitter Takashi Kawamura, and the friendly but competitive Takeshi Momoshiro. Most significantly, he catches the eye of the stoic and nationally-ranked captain, Kunimitsu Tezuka, who sees both immense potential and a troubling flaw in the boy's game. Ryoma proves his skill in the monthly ranking tournament, becoming the only first-year student to earn a place on the regulars team just as the regional preliminaries begin.

In a crucial match against Fudomine Middle School during the regionals, Ryoma injures his eye but his determination to finish the fight helps Seigaku secure victory and advance to the Kanto Tournament. Captain Tezuka, however, is deeply concerned. He recognizes that Ryoma perfectly copies his father's playing style, a path that will prevent him from developing his own tennis identity. Tezuka also worries about his own chronically injured arm. In a secret match against Ryoma, Tezuka disregards his physician's advice and uses his devastating Zero Degree Drop Shot to defeat the prodigy soundly. He then delivers a critical lesson: Ryoma must forge his own unique style of tennis and become the pillar that supports Seigaku.

As the Kanto Tournament approaches, Ryoma struggles with his purpose and considers returning to America. He encounters a quiet, mute girl named Shioin Higaki, who watches him from the bleachers and communicates through a flute. Ryoma ultimately decides to stay and compete. Seigaku faces their powerful rivals, Hyotei Academy, led by the flamboyant and supremely confident Keigo Atobe. The team faces a series of grueling matches. The doubles pair of Oishi and Kikumaru, known as the Golden Pair, barely loses. In a brutal singles match, Kawamura trades dangerous Hadokyuu shots with his opponent until both are unable to continue. Fuji effortlessly wins his match 6-0. The tournament comes down to the final singles match between the injured Captain Tezuka and Atobe, followed by a decisive tiebreaker between the reserve players. Tezuka sacrifices his arm to push Atobe to the limit but ultimately loses in a tiebreak. With the overall score tied, the championship rests on a final match between Ryoma and a formidable Hyotei player, Egate Mcleod Higaki, who is also Shioin's brother.

As an eclipse passes over the court, Higaki uses a brutal style that injures Ryoma's leg. Remembering his vow to become stronger and develop his own tennis, Ryoma rallies, surprising everyone with his new attack, the COOL Drive. He breaks through Higaki's intimidation tactics and wins the match, securing Seigaku's victory. As Ryoma looks toward the stands at their future opponents in the national tournament, his only response to the challenges ahead is a confident "mada mada da ne," indicating he has a long way to go before he reaches his peak.