Shusuke Fuji is a third year student at Seishun Academy,He is given the title 'tensai', or genius, due to his tactical skill on the tennis court. He is in the same class as Eiji Kikumaru, and is Eiji's good friend. Fuji is cheerful and easygoing, with a penchant for playfully teasing those around him.

He grew up in Chiba, where he became friends with Kojirou Saeki, the current vice-captain of the Rokkaku Chuu Tennis Club. Later on, he moved to Tokyo and entered Seigaku.

Fuji usually takes the position of S2, although sometimes he is paired w/ Takashi Kawamura or Eiji Kikumaru in Doubles. He also temporarily takes the position of Singles 1 when Kunimitsu Tezuka is in rehabilitation.

Along with Tezuka, Fuji is possibly the only person on the entire Seigaku team who is immune to Inui Sadaharu's various concoctions. However, while Tezuka only appears unaffected and does not state what he thought of the concoctions, it has been a running gag in the story that Fuji actually "likes" those drinks and will recommend others to it too. While he may occasionally intentionally fault in practice in order to try the penal concoctions, he has also mentioned that he enjoys seeing others suffer from drinking the concoctions even more. He is, however,not immune to "Aozu", a horrific blue vinegar and cod liver oil concoction; this drink causes his only blackout, and since then Inui has believed that Fuji has a grudge against him. His odd tastes in food do not stop at Inui's gruesome health drinks, and he takes delight in wasabi rolls, honey-mustard and horseradishes.

At times, Fuji tends to act like Eiji Kikumaru--he wants to win and to be number one. In one episode, there is mixed club day at his school. On this day, the students are not allowed to play the sport that they are in. For example, the "Golden Pair", Eiji Kikumaru and Shuichiro Oishi, plays volleyball. Fuji plays curling, which no one else plays. His words are, "No participants; the championship is mine" ^_^

Special techniques

Counters

Sometimes called the "Three Counter Moves" (or more often called the Triple Counter). Game sealing returns, the counters are techniques that could only be pulled off by a genius like Shusuke Fuji. Each counter has a very low chance of being returned.

Later on in the series, during the Nationals, Fuji upgrades his Triple Counter and reveals more counters: Kagerō Zutsumi, Hecatoncheires no Monban and Hoshi Hanabi.

Although Fuji develops six counters, his set of counters is still called "Triple Counter".

Fuji's counters are based on animals:

Tsubame Gaeshi: Swallow
Higuma Otoshi : Brown Bear
Hakugei : Whale
Kagerō Zutsumi : Dragonfly

When Fuji "evolves" his Triple Counter, their new names are based on mythical creatures:

Houou Gaeshi : Phoenix
Kirin Otoshi : Qilin
Hakuryu : Dragon