Eiji Kikumaru (菊丸 英二, Kikumaru Eiji?) is part of Seigaku's "Golden Pair" along with Oishi. He uses "Acrobatic Play", which takes advantage of his flexible body. Eiji is also known to have the sharpest vision on the team, with an exceptional talent for seeing moving objects. Eiji's main weakness, however, is his lack of stamina, which he overcomes through hard work and training later in the series. Though the Golden Pair seldom play without each other, circumstances such as their temporary breakup when Oishi gives his spot to Ryoma, forces him to play in singles. Eiji is a friendly, sweet-tempered and outgoing character and the youngest of a large family. He is voiced by Hiroki Takahashi in Japanese media, voiced by Steve Staley in English media, and portrayed by Osamu Adachi in the live-action film.

Eiji's flexible body allows him to reach balls with a touch of flair that few can replicate. His graceful dives and flips astonish the spectators and often gets grudging praise from his opponents, which helps Eiji focus. He focuses on the net with his "Kikumaru Beam", a sharp volley that is hit with his hand reaching around his back, and his "Kikumaru Bazooka", a smash hit upsidedown. While playing doubles, Eiji follows the lead of Oishi. The two rely on and know each other thoroughly, which allows them to predict each other's moves without any signals. They further develop this by achieving "Syncronization", letting them act together as if they were only one person. He can also play well in singles by using his "Seal Step", which uses his speed to move from one location to a new one the moment the opponents eyes leave his first location. This gives the opponent the impression that there are two of him for a doppelganger type effect, though the anime gives him the ability to hug and high five his after image, making it slightly unrealistic.