Masashi Arai (荒井将史, Arai Masashi) is a 2nd-year student at Seishun Academy. He is a member of the Seigaku tennis club and is usually seen with Ikeda and Hayashi, also 2nd-years. He is introduced as rash and arrogant player, though he is proud of his team and respects the regular lineup. He is often seen cheering for Seigaku during its important matches. He is probably Seigaku's best non-regular player.

Arai tries to get back at Ryoma by stealing his tennis bag and challenging him to a match, offering an old wooden racket as a replacement. Despite this, Ryoma effortlessly mauls Arai until the match is stopped by captain Tezuka Kunimitsu.

Arai has ambitions about being in the regular lineup and realizes he is unlikely to gain a spot when Ryoma sweeps the Seigaku monthly ranking tournament. He most likely earns a regular spot in his third year due to a number of graduations and Ryoma's departure from Japan.

Anime Only EventsEdit

Arai and his friends try to extort 1st-year students Horio Satoshi, Katō Kachirō and Mizuno Katsuo by enticing them to knock over a can of tennis balls with a serve and charging a fee. Horio manages to hit the can, but is unable to knock it over due to Arai rigging the can by filling it with rocks. Arai challenges Ryoma Echizen to take part, but is humiliated when Ryoma reveals Arai's tampering, knocks over the can with a direct hit on the top and hits the can with ten consecutive serves.

When several of the regualrs are injured from the Hyoutei match, Arai see his chance to make it as a regular. He is challenged by Katō Kachirō, who demands that Arai earn the spot in the proper way while promising to leave the club if he loses. Despite Kachirō's lack of skill and experience, Arai goes all-out to the surprise of his friends. The match is stopped by Oishi and all participants are ordered to run laps. It is revealed that Arai had been wearing one too many ankle-weights during the match, as Inui corrected afterward. Kachirō realizes Arai's honest intentions, and Arai affirms that he intends to earn his way to the regular lineup.