Uselessly Handsome Guy 
14 (The Prince of Tennis)
Rokkaku Junior High (3rd Year)
Rokkaku Third Primary School
Serve and Volley
Made by Ojī
NIKE NIKE AIRCOAT Implosion MID (F302228 041)
Katsuaki Arima (Japanese)
Kojirō Saeki (佐伯虎次郎, Saeki Kojirō) looks really laid-back and gentle, but looks can be deceiving, for he really is a very dangerous player. His talent for tennis is natural, and is accompanied by his above-average sight, which makes him even more difficult to beat. Saeki is also Rokkaku's Vice-Captain, and like Aoi Kentaro, seemed to be randomly selected by their coach. He was also the childhood friend of Shūsuke Fuji, and is still good friends with him.
He has soft laid back light brown hair and brown eyes. In the anime his hair is two toned with the top layer being a silver-white and the bottom layer being black. More than once during the series, he was described to be good looking by various characters. During the one of the PairPuri episodes, it was shown that his looks and gentle demeanor attracted girls.
Gifted with incredible motion vision and a natural sense of the sport, the laid-back Saeki makes for a very dangerous opponent. He is a very friendly guy who is nice even to strangers. Due to his thoughtful personality and good looks Saeki is very popular with girls (much to the envy of his junior Aoi). He does not really care for popularity and prefers to treat everyone equally. His natural charm and the fact that he also quite good with words is what draws women to him (according to Shitenhoji's Konjiki).
In the Prince of Tennis Musicals he is portrayed as a cheerful and carefree guy who smiles a lot. He almost comes across as a joker who loves to lightly poke fun at people (especially Fuji).
Saeki is first seen in the company of his fellow Rokkaku regulars observing the Seigaku-Hyoutei match. It is at that time that he and Marehiko Itsuki decide to pair up to play doubles after Amane "David" Hikaru refused to play against Shūsuke Fuji.
Just prior to Rokkaku's match against Seigaku, Saeki informs Shūsuke Fuji that Rokkaku's current captain is a freshman. Fuji in return yells at him and telling him that a first year captain is not something to laugh about.
During the early stages of the Kantō semifinals, with his potential reaching its climax, Saeki completely blew past Eiji Kikumaru, whose versatile Acrobatic Play became a non-factor. Despite a fabulous start against the Dream Pair, Saeki and his partner Marehiko Itsuki were unable to keep up when Kikumaru unveiled his Seal Step, and dropped the match to Seishun Academy. The doubles lineup also gave Saeki and Shūsuke Fuji a rare opportunity to confront each other on the courts. Saeki is a good friend of the Fuji brothers and is aware of the tension between Shūsuke and Yūta Fuji. He said that when he played Yūta he purposely lost as not to injure Yūta's shoulder any further by continuing the match. Because of his analytical ability, Saeki dictates the play for Itsuki during the key points. He also devised a strategy to seal off Yūjirō Kai's Shukuchihō.
In the middle of his match against Higa's Kai Yūjirō in Singles One, his opponent mercilessly directed a shot against Oji, sending the old man to the hospital, after hearing Oji's insights about the Shukuchihō. Armed with new knowledge Saeki proved to be stronger than his opponent, but Kai still won the game, and emerged as winner, thus giving another point to Higa Chuu.
Playing Style and Techniques
Saeki is a very skilled player and is easily able to see opponents patterns and find a weakness. When in doubles, he also advices his partner, Itsuki, at certain times to change the flow of the game.
Australian Formation (Anime Only)
In episode 136: Junior Selection Camp, Gathered, Fuji and Saeki pair up as a doubles pair against Inui and Yanagi pair. When they were losing, both Fuji and Saeki surprised viewers with their ability to use the Australian Formation. This allowed Fuji to use his first counter, Tsubame Gaeshi, in the match.
- Favorite Food: Mashed bean curd, Roast sea urchin (midraw)
- Hobby: Sea Activities
- Father's occupation: Engineer
- Uses Money On: Western clothes
- Motto: One chance, one shoot, one kill!
- Favorite Subject: Social Studies, Japanese
- Worst Subject: Math
- Committee: Vice-President of Student Council
- Most Visited Spot in School: Banking fence by the sea
- Favorite Color: White, Beige
- Favorite Movie: Titanic
- Favorite Book: King Lear by William Shakespeare
- Favorite Music: Chanson (French songs)
- Preferred type: A girl who can control/restrict me (Because she can't put me aside)
- Date Spot: Resort
- What he wants the most: To raise a dog
- Daily Routine: Walking along the beach
- Dislikes: Narrow places
- Other talents: Doing artistic castles of sand
- In Musical, he is played by Kanata Irei. In New Prince of Tennis is an character named Irie Kanata, which his name is taken from.