|Age|| 15-16 (series run)|
18 (final chapter)
|Height||159 cm (5'2)|
|Bench press||60 kg|
|Affiliation||Seibu Wild Gunmans|
|40 Yard Dash||4.5 seconds|
|Position|| Running back|
|Team|| Seibu Wild Gunmans|
Enma Fires (university)
|Japanese|| Yuuki Masuda|
Chikiri Kyoko (younger)
"A guy bumps into a girl and says she's in the way? You're pathetic." -Riku Kaitani
Riku Kaitani (甲斐谷陸 Kaitani Riku) is the Running Back for the Seibu Wild Gunmen and an childhood friend Sena who taught Sena how to run
Riku is short, similar to Sena and Monta. He has short, white hair which spikes upwards and blue eyes. He is more muscular than Sena, as he has more experience fighting then Sena, who actually never fought back when bullied.
Riku is seen as a genuine good guy, stopping bullies and anyone else who he sees in the wrong. This is seen when he stops the bullies from bullying Sena and twists the arm of a guy who bumps into Mamori telling her 'You're in the way'. In some ways, he is also confident in his abilities and sometimes becomes arrogant. He also is very willing to help people, as he teaches Sena how to run and also teaches Shin Seijuro the Rodeo Drive. Riku seems to regard Kid as an almost idol, often referring to him as the "best quarterback" and standing up for his talents when Kid himself won't. Kid usually calms him down by putting his hat on Riku's head.
When Riku was in elementary school, he saw Sena being bullied and he used his speed to save him. Riku told Sena that he shouldn't have to deal with the bullies and he should stand up to them. Sena pointed out that unlike Riku he had never fought before and he was weak so Riku told Sena he was going to teach him speed as a way to fight the bullies because with speed you have an advantage in avoiding attacks. So Riku taught Sena how to run as a way of building up his speed. After days of practicing Sena finally learned how to dash and run fast. Sadly, Sena used his speed to be a gopher, (though it's ironic that being a gopher is what helped build up his speed). Riku soon left Sena's school because his family needed to move. In the anime, he and Sena made two promises. One was that Sena would always run. The second was that Sena would protect Mamori. Before he left, Mamori gave him a cat charm she made (Sena and Riku thought it was either a pig or a horse), which he wears around his neck in a pouch. It was shown that Mamori made one for herself and Sena, which Mamori keeps in her schoolbag, and Sena hangs on his lamp at home.
He and Sena meet again, six years later in chapter 127. Like Shin, he was able to quickly deduce Sena's identity as Eyeshield 21 (he was furious when he heard that Sena stayed being a gopher though). When his team went up against the White Knights, Riku proved to be no match against Shin and was unable to get by him once.
During the Kanto Tournament, Riku faced off against Gaō when he was about to beat up, possibly kill a fan who had insulted Banba, (and anyone else who was in the way). Fortunately, the incident ended without any bloodshed. After the Seibu Gunmen devastate the Misaki Wolves with a score of 48-21, they now prepare to face off against the Hakushū Dinosaurs in the semi-finals.
Before the match between the Strong Golems and the White Knights, Shin approached Riku and asked him for the secret of the Rodeo Drive. Initially he refused, thinking that Shin had already defeated him during the Tokyo Fall Tournament and that he didn't need such a technique. However, after learning that Shin is actually acknowledged him for his technique and that he will shows no hesitation if Riku or Sena asked him about his technique otherwise, Riku admitting his own hypocrisy and agreed to show him, thinking that Eyeshield 21 might be the one to beat him. His prediction proved true as Sena gets past Shin in the final second of that game to win. Afterwards, he and Sena meet up with the Dinosaurs' manager who urges both teams to surrender during half-time as she does not want to see any more people hurt. Riku is not intimidated and is determined to face off against Sena in the Kantou Final. However, as the Dinosaurs begin increase their pressure on the Kid, that goal became more difficult to realize. With the loss of both the Kid and Tetsuma, the dream becomes impossible as the Gunman lose out in the semi-finals.
Afterwards, Riku shows up in Deimon's base, sporting a new haircut, steals the ball from Taki before he realizes it and becomes Deimon's trainer for their special training for Christmas Bowl. He is training Ishimaru, draging him along with ropes to increase his speed and stamina, also teaching him Rodeo Drive, which Ishimaru uses at the Christmas Bowl. Riku also goes to see the Deimon Devil Bats win the Christmas Bowl and roots for them. Not long after, he is recruited to travel to America to represent Japan for the Youth World Cup, playing as safety. Two years later, Riku attends Enma University and plays on the football team with Sena and other players from various teams from high school. When Unsui asks Riku why he didn't go to Saikyoudai University, where he could have easily gotten in with his athletic ability and grades, Riku answers that he joined Enma University because he had a desire to defeat the strongest, a phrase that he picked up from Sena when Sena considered going to a football team different from Hiruma so he can attempt to defeat Hiruma at football.
- Rodeo Drive - Riku's signature technique, which he employs by using a "stiff-leg" running style while leaning his upper body forward in quick spurts, giving him explosive acceleration for seconds, therefore, making it difficult for the defense to read his step pace. He uses this technique to make an immediate statement at the start of game against the Devil Bats by returning the opening kickoff for a touchdown. He also uses this technique to stop opposing runners, by using the acceleration power he gained to push his enemies down. However, it is not effective against Shin's Spear Tackle nor Sena's Devil Bat Tornado.
- Roping Rodeo Drive (manga only) - After discovering Gaō's tactic of scaring the quarterback into submission, Riku begins developing a new version of the Rodeo Drive, which allows him to weave and turn without stopping, much like Sena's Devil Bat Ghost. Marco explains that the technique is merely a combination of the Rodeo Drive with swerving, stepping in circular form (thus the name "Roping"), similar to the maneuver of rugby players to get down the field without being tackled. However, this was proves useless, as Gao didn't even care about his target makes feints or not, he'll just go forward crush him with all his might.
- Rodeo Drive Stampede (anime only) - During the Misaki Wolves vs Seibu Wild Gunmen game, Riku shows an advanced version of the Rodeo Drive, the Rodeo Drive Stampede. This technique is employed by using the rugby technique "Change of Pace" with rapid cuts, allowing Riku to create four clones of himself, running past opposing players.
- Sena's top speed for a 40-yard-dash is 4.2 seconds, while Riku's is 4.5 seconds.
- However, Riku can run at his top speed for long periods of time, while Sena's normal speed during a match is 4.5 seconds, making them roughly the same in terms of speed in a real game but later on Sena normal speed became 4.2.