Sena Kobayakawa is the protagonist of our story and the Deimon Devil Bats’ fleet-footed runningback, better known by his enigmatic codename, “Eyeshield 21.”

A kind-hearted, timid people pleaser with an unusually short build, Sena spent most of his life being taken advantage of by others. Since kindergarten, he's acted as a gofer boy for every bully he’s encountered: fetching snacks from the school store, carrying backpacks…you name it, Sena has probably done it to avoid getting beat up. As a result, he's developed both cowardice and extreme conflict avoidance: placating others with nervous rambling, unnecessary apologies, yelping loudly, and running away at the first sign of danger. Although his childhood friend Mamori sometimes protected him, he's always wanted to become brave and independent. All of this said, Sena’s small body and self-preservation instincts have helped him in one special way: he's developed superhuman speed and agility, making him an incredibly nimble runner.

During an impressive escape from a trio of delinquents on his first day of school, Sena’s “golden legs” caught the attention of Youichi Hiruma, the Devil Bats’ fiendish quarterback, who then recruited him as the team's ace running back. He christened Sena “Eyeshield 21," equipped his helmet with a tinted visor, and billed him as a legendary athlete from the University of Notre Dame. This not only protects Sena's identity from sports clubs wanting to scout him, but boosts the Devil Bats' image to stronger teams. It also ensures that Mamori, who's incredibly overprotective of him, doesn't find out that he's playing American football. It's an absurd setup that Sena resents at first; he openly wonders if this is just an extension of the gofering he's always done before. But as times goes on, he starts to enjoy playing, and even begins growing into the Eyeshield 21 persona.

Due to the militaristic nature of American football, Sena routinely competes against players bigger, stronger, and far more aggressive than he is. Initially, Sena went into games riddled with dread, and was ready to duck out as soon as it got too scary. But during the Devil Bats' game against the Oujou White Knights, a competitive streak awakened within him as he tried and failed tirelessly to outrun their ace cornerback Seijuurou Shin. He found that his legs grew faster with each play, and his resolve strengthened with each attempt. Although they suffered a blowout loss and were eliminated for the spring season, Sena managed to succeed at the very end, leading Shin to not only recognize him as a worthy rival, but vow to face him again in the fall season's finals. Thus began the journey that would chart Sena's steady growth into a capable athlete: each rival leads him to run faster and to try harder until he comes out on the other side victorious, with more opponents that respect his skills. As he continually trains and practices with his teammates, he finds that the absurd bluffs and lies Hiruma uses to hype him up to others are starting to come true.

Thanks to his size, speed, and determination, Sena can outrun and outmaneuver other players in ways they themselves cannot, even when it takes frequent attempts to do so. He also develops several different techniques that allow his body and legs to overcome even the most persistent opponents, most notably the Devil Bat Ghost cross-step, Devil Bat Hurricane spin move combo, and the risky Devil Bat Dive. Sena's growth as a capable athlete also extends to him as a person. While he still has moments of lacking confidence and denying any compliments he receives with bashful bows and ramblings, he grows less prone to running away when confronted by a potential threat, and matures significantly in how he approaches conflicts and obstacles. He also becomes a better friend and more altruistic by standing up for others and helping them both friends and strangers alike when they need it the most. While it takes him time, courage, and resilience, Sena has found both friendships and personal growth in playing as Eyeshield 21. While this isn't a fate he chose for himself, it's one that's opened him to more people and possibilities that he never could have imagined.

Sena's Height, Weight, and Power stats are significantly low, consistent with his short, delicate physique. While he does eventually build muscle the stronger and more physically active he gets from practices, he still isn't the go-to player for anything strength-based. His mind also isn't especially sharp, hence his average-to-low Intellect stat.

Unsurprisingly, Sena's Speed stat is his strongest. Between years of playing gofer for bullies and his tiny, lightweight body, Sena is incredibly agile. He can outrun most opponents and weave his body in ways that would be more difficult for taller, heavier players. He can also squeeze himself through gaps in the line of skirmish that would usually be too tight. Additionally, his Technique stat is slightly elevated thanks to learning several techniques that use his speed, agility, and small size to his advantage.

Devil Bat Dive

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Devil Bat Ghost

The Devil Bat Ghost is a cross-stepping play, developed with the help of Coach Doburoku to help combat Sena's tendency to hesitate right before running past an opponent. During the Devil Bats' "Death March" training in the Southwest United States, Doburoku has Sena kick a rock while running down the interstate highway behind his teammates to help him develop a rhythm where he won't hesitate. From this, Sena learns to add a cross-step that will better maneuver his body around the opponent as soon as he gets close. Since Sena is running at such a high speed, it gives the illusion that he's passing right through the opponent's body, like a ghost passing through a wall.

Devil Bat Hurricane

A slightly modified version of the Devil Bat Ghost, but with a spinning move in which Sena twists his body counter-clockwise while weaving around the opponent and resuming his run. This was the same spin move he used when dodging Toganou when fleeing from the Hah Brothers during his first day of school, and Kuroki calls back to it while Sena is struggling to avoid Shun Kakei of the Kyoushin Poseidons.

Mihae Kobayakawa (mother)	Shuma Kobayakawa (father)	Pit (pet cat)

In Japanese, Sena's surname Kobayakawa (小早川) literally means “small, fast river," thematic to his speed and agility.

The kanji in Sena's name (瀬那) can be taken apart to mean “stream” or “current” and an archaic way of spelling “What?" One could read it as expressing surprise at a river's fast-moving current, as Sena's opponent's often do at his speed. According to Riichiro Inagaki, Sena was named after the famous Brazilian race car driver, Ayrton Senna da Silva.

Miyu Irino

In the 2005 anime series, Sena is played by Miyu Irino. He started voice acting from a young age, and tends to play youthful guys with calm sounding voices. Some of his other roles include Sora from the Kingdom Hearts video game series, Haku from Spirited Away, Ritsu Kageyama from Mob Psycho 100, Todomatsu Matsuno from Mr. Osomatsu, Koushi Sugawara from Haikyuu!!, and Syaoran Li from Tsubasa Reservoir Chronicle.

Romi Park

Romi Park voiced Sena in the 2003 Jump Festa OVA, The Phantom Golden Bowl, and is a widely recognized voice actress who has won multiple awards for her work. She’s best known for playing brash young boys and tough, deep-voiced women. Some of her roles include Edward Elric from Fullmetal Alchemist, Tao Ren from Shaman King, Temari from Naruto, Toushirou Hitsugaya from Bleach, Hange Zoë from Attack on Titan, and Nana Osaki from Nana.