Sena Kobayakawa, also known as Eyeshield 21, is the main protagonist of the Eyeshield 21 anime and manga.
Sena entered highschool always running away from and running errands for bullies, which gave him very remarkable foot speed. Very soon, Sena's talents were noticed by the highschool's Shadow Dictator, also captain of the two-man American Football team "Deimon Devil Bats".
At first, Sena played football only because of being forced by a certain insane quarterback. However, after his encounter with Seijuro Shin in the Spring Tournament, he came to the realization that playing football was the first time he actually did something worthwhile with his life, and developed the desire to make himself stronger in order to face Shin again. As more players joined the Devil Bats enabling him to engage in more and more football plays, Sena even started to LIKE playing American football. For the Devil Bats, the recruitment of Sena was the true beginning of the team.
Sena, for his part, grew to seriously love american football, to the point that he voluntarily participated in the Death March and even joined Team Japan for the Youth World Cup. At the end, Sena proved to be impressive enough that he was invited to play football in Notre Dame, truly becoming "Eyeshield 21". The finale showed that Sena went to the Enma University after highschool, and was aiming at becoming a professional football player after college.
In the AWA fics, Sena is a student at the AWA Academy.
Sena is a rather short and somewhat frail high school student, and is overall so weak that he is frequently dragged or carried around against his will at the beginning of the series. He grows somewhat taller and more muscular as he physically grows through the course of his first year in high school and also trains his body by playing football. His hair is dark brown. However his hair also seems to be naturally spiky and sweeping up and to the left, judging by how his hair had the same shape when he was a child.
While playing football he wears a green eyeshield. Just before the game against Bando he discarded his green eyeshield and revealed his identity, this being the only time he played without an eyeshield. After the Bando game he started using the blue eyeshield previously worn by Hayato Akaba that he was given. In the anime he went back to using his green eyeshield and never used Akaba's blue one.
Sena has been an extremely timid pushover for his entire life often been protect by Mamori and often forced to act as errand boy to avoid getting hurt by Bullies. This begins to change as he matures through the series, largely due to his experiences playing American football. While Sena remains fearful of injury and is easily intimidated for the duration of the series, he becomes more courageous and willing to place himself in danger, either for the sake of helping his team win or to protect others.
Sena is sometimes considered to be chivalrous by his friends because he most often ends up protecting women and children. Sena quickly takes a liking to American football after he begins playing it, and is particularly thrilled whenever he is able to compete against other strong players. When he is not playing football, he is usually shy, modest, and reserved, even when he has accomplished amazing feats and become famous. Sena rarely acts confidently and never boasts about his abilities, and whenever he attempts to make a bold statement, he tends to trail off at the end as his own self-doubt and fear cause his countenance to fall apart.
Sena does not usually grow angry, only doing so when people insult the hopes and dreams of others or begin to give up on their own dreams such as Agon insult Hiruma and Kurita dreams of going to the Christmas Bowl. Sena's doubtful outlook usually contrasts with those of his more confident and reckless friends and teammates, such as Monta and Suzuna. Despite this negativity, which can be a bit annoying sometimes, Sena always becomes determined in the crucial moment of a match when he must surpass an opponent with superior abilities and could be said to act appropriately when it matters most.
Sena's greatest talents as a football player are his speed and agility, which combined make him one of the fastest high school players in Japan, and even the world. All of Sena's techniques stem from his ability to run at incredible speeds and rapidly change the direction he is running in. At first, Sena is only able to maintain his full speed, which allows him to run a 40-yard dash in 4.2 seconds, in brief bursts, and he tires quickly after doing so. With time, he improves his stamina and is able to maintain his top speed for extended periods, although constantly doing so places great strain on his legs in the match against Shinryūji. After receiving instruction from Doburoku, Sena learns to change direction without decreasing his speed using a technique called the Devil Bat Ghost. Sena improves this technique on his own, creating a number of sub-techniques including the Devil Bat Hurricane (a spin move) and the faster Devil Light Hurricane. Sena is also the most frequent user of the Devil Bat Dive, a strategy that the Devil Bats frequently use to finish games in situations where they start the play just outside of the end zone and Sena dives over the line in order to score a touchdown.
Throughout the Devil Bats' games, Sena has used the Sky Devil Bat Dive, in which he jumps into the air before receiving the ball, the Twin Double Bat Dive, in which both he and Monta leap and Sena has the option to pass the ball to Monta, the One-Man Devil Bat Dive, in which he jumps over a single defender in a direct confrontation, and the Cerberus Dive, a variation where three different players dive forward while only one carries the ball. The final running technique that Sena develops is the Devil 4th Dimension, a backstop that he performs at full speed immediately after charging straight at an opposing defender; this allows Sena to dodge away from a defender when they dive in to tackle him. Furthermore, Sena is able to combine the Devil 4th Dimension with the Devil Bat Ghost, which grants him the ability to freely move in any direction on a 360-degrees axis without once decreasing his speed.
While he is initially very scrawny, Sena's physical training along with the natural course of his growth grant him enough physical strength to compete against his opponents, using his power when he is unable to dodge around them. He most frequently does so using a chopping technique called the Devil Stungun, which he uses to deflect his opponent's arms when they attempt to tackle him. Sena can also use stiff-arms to push away his opponents, and has even managed to shove players of superior physical strength to the ground when doing so. While Sena primarily plays in the running back position, he has on occasion played as quarterback, most notably when Hiruma was injured in the match against Hakushū. Sena's throwing technique is very unrefined, but he is adept at scrambling using his great speed and can use this to open up plays, allowing him to choose to run or throw the ball.
It should also be noted that Sena has surprisingly good balance, able to run on top of the railings of overpasses and highways (even when drunk). He has often shown great dodging abilities as well, such as the time where he avoided every item that Torakichi threw at him from a near point-blank distance, as well as the time he dodged Agon's thrown football that was aimed directly at his right eye. Ikkyu also noticed this, noting that Sena had used the minimum amount of movement to dodge.
Normal Running & Cuts: This was Sena's method of running at the beginning of the series, gained during years prior when he was a gopher for bullies. He is able to attain a rocket start, as well as make very sharp turns and cuts. However, his speed decreases after the explosive start so, before training with Deimon, his 40-yard-dash is 5.0 seconds. If he's pressed to a certain emotional level, (such as being chased by Cerberus or Shin), his time shortens to as little as 4.2 seconds (see Speed of Light Pace).
- Change of Pace: This was Sena's pattern of running up until after the game of the Nasa Aliens. This involves him running at relatively easy pace, then suddenly accelerate to full speed. The problem with this is that just before he speeds up or makes a turn, he stops for a moment, which allow others to tackle him.
- The Devil's Cut: A skill that allows Sena to keep his pace after changing direction (in which he moves at his full speed). Initially, Sena had to stop before changing directions through his sharp cutting ability in his movements, but after the Death March, in which he had to maneuver while kicking a rock while keeping pace with his full speed, he developed The Devil's Cut. Ultimately this technique overcame the old Change of Pace and allowed Sena to keep running without losing any speed making him a better runner as a result. With this he learned the Devil Bat Ghost.
- Speed of Light Pace: This is Sena's ability to run the 40-yard dash in 4.2 seconds, considered to be at the highest level even among professional athletes. Initially, he is only able to tap into this speed once per game, as it totally exhausts him after using it. However, in the match against the Bando Spiders, he manages to overcome his limits and manages to hold his top speed for a much longer period of time (though he still collapses after the match). By the beginning of the Kantou Tournament, Sena is able to run at this pace frequently without rest. First used in a match against the Ojo White Knights during the spring tournament.
- Speed of Super Light Pace: Shin estimated for Sena's Final Play against him that he was able to run a 40-yard dash in 4.1 seconds. He achieved this by using Shin's arm as a propellant. Its name was christened by Shin, and is only used in the final play against the Ojo White Knights in the fall tournament.
Foresight: A technique first developed for running errands, Sena is able to deduce the amount of movement, as well as any openings his obstacles (often people, such as the opposing team's players in an on-going game) might leave unguarded (or about to), and thus effectively discern the directions needed to escape a tackle or breakthrough defense while he's running. He first uses this technique in actual gameplay against the Koigahama Cupids team when he returns the final kickoff of the game for a game winning touchdown, making the skill very handy in slipping through large numbers. This also helps him to determine which way he could play being a quarterback, either to do a pass or run. However, its main weakness is that it can't anticipate the moves of an incoming opponent if they are moving at the same rapid pace as Sena at his topmost speed, forcing Sena to improvise when facing other speedy players like Shin, Riku or Panther. Used frequently in games (typically represented graphically as arrows of light).
- Scramble and Pass: In the quarterback position, Sena takes the ball after the snap and rushes toward the sides. He then makes a short, awkward pass toward any eligible receiver. The trajectory of the ball is described as horrible by Ikkyu, though in practice it works for Sena, as the opponents can't tell which way the ball is heading. This is somewhat similar to the halfback option play in the NFL. Used only against the Hakushuu Dinosaurs.
- Devil Dragon Fly: An adaptation of Shinryuji's trademark play, both Sena and Hiruma play as quarterbacks. Either quarterback is able to receive the snap, and the number of plays, such as lateral passes between quarterbacks and passes to receivers, are increased greatly as a result. Unsui comments that the way Deimon played this formation is different, but definitely has the shape of the Original DragonFly. The players can work this tactic perfectly thanks to amount of Spartan practice (physical and mental) they've been through. Used only against the Hakushuu Dinosaurs.
Chris Cross: Another variation of running play, Monta and Sena cross paths with the quarterback (Hiruma) as their center. This hides the true ball carrier, as any of the three players may have the ball after crossing (hence the name of the play). Due to Sena and Monta's initial inexperience with the play, their first use of the Chris Cross results in a fumble. Used twice, and only against the Teikoku Alexanders.
- Devil Cross: The "warped" version of Chris Cross, in which the ball carrier laterals the ball toward the quarterback after luring the defense, giving the pass play more options and freedom.
Devil Bat Ghost: A technique in which Sena is able to use a crossover step to make a sharp cut without slowing down. He learned this after enduring the 2000 km Death March by kicking a stone pebble and running simultaneously (and, by doing so, learned how to increase his steps without losing his speed). Its effect creates a kind of blurry afterimage which confuses opposing blockers, causes them to misjudge his speed or tackle the afterimage created by the move. By episode 46 of the anime, in a match against Shin, Sena discovers the strain of the Devil Bat Ghost has on his knees, which he soon overcomes with constant practicing and soon Sena is able to use Multiple Devil Bat Ghost Bursts. Later, his Devil Bat Ghost evolved so much, that he is practically creating shadows and moving in a complete 360 degree range at will, making him nearly impossible to touch. Just like Shin said, "Even with all power in this world, it's no use against a speed you can't touch".
- Multiple Devil Bat Ghost: In chapter 287, after witnessing "true" Ghost Steps performed by Yamato, Sena manages to perfect his own Devil Bat Ghost using a combination of violent crossover and simple cut steps, creating four "clones".
Devil Bat Dive: Inspired by his desperate dive into a closing train to escape from the Hah Brothers in the first chapter, Sena rushes toward the scrimmage line at top speed, then jumps over the opposing linemen in a corkscrewing motion. This is a very dangerous maneuver and even Hiruma initially forbids him to use it more than once or twice per game, and only for a clinch point, as it could easily cause injury to Sena. Used on occasion during various games.
- Sky Devil Bat Dive: An alternate version of the Devil Bat Dive, Sena is first placed at the end of the scrimmage line. Hiruma rushes the opposing line as Sena makes a fast reversal; once Sena gets up to speed, he jumps upward as Hiruma laterals the ball to him.
- Fake Devil Bat Dive: Unlike the regular Devil Bat Dive, this involves Sena jumping over opposing players while pretending to carry the ball. The technique is intended to fool the opposing team in stopping his charge while the real carrier of the ball gets through. This was first shown during the game against the Wild Gunmen, and last seen against the Dinosaurs.
- Double Devil Bat Dive: Sena rushes toward the goal line then jumps over the defending linemen like in a regular Devil Bat Dive, but then passes the ball in midair to Monta who is in the end zone. Used only against the Ojo White Knights during the fall tournament.
- One Man Devil Bat Dive: Sena dives over a single opponent. In its first use against Shin Seijirou, it was used in tandem with the Devil Stungun and Devil Bat Ghost. He uses this move in the last play against the Ojo White Knights in the fall tournament, and again against the Teikoku Alexanders.
- Extremely Low Altitude Devil Bat Dive: A combination attack with Komusubi, using the small lineman's power and Sena's ability to fly over a low-gravity opponent such as Gaou. Used only once against the Hakushuu Dinosaurs, and succeeds only when Kurita intervenes to prevent Gaou from crushing Sena and Komusubi.
Spin Move: A regular move which Sena used to evade Togano in the first chapter. While running forward, he evades enemies' tackle or block by swerving to the side and spinning his body to gain momentum he needed to break/escape the block/tackle.
- Devil Bat Tornado: Also called the Devil Bat Hurricane, this was created during the game against the Kyoshin Poseidon by combining the Devil Bat Ghost with a Spin Move. Its effect not only causes an afterimage to appear, but also adds rotational force, making a two-handed tackle (like Shun Kakei's "anchor-grapple") less effective.
- Devil Light Tornado: Also called the Devil Light Hurricane, this is basically combining the Devil Bat Tornado with the Speed of Light Pace. In chapter 217, he uses this in an attempt to evade Shin's Trident Spear Tackle. However, Shin, with his own Speed of Light Pace and the extra speed of the Trident Tackle, manages to down Sena. It is also not as effective against close defensive attacks such as Marco's Screw Bite.
- Vertical Devil Light Hurricane: Sena collides into his opponent head-on, then pushes upward while rotating at the Speed of Light Pace. Using the opponent's body as a pivot, Sena rolls past and forward, thereby evading any attacks. Being so close prevents an opponent with a close defensive attack (like the Screw Bite) from getting his hands around the ball.
Stiff-Arm: A normal defensive move used to keep an opposing player at a distance. By sacrificing ball safety, Sena can extend one arm to ward off a blocker. First done against Agon in the game against the Nagas, Sena was able to topple him by pushing against Agon's helmet.
- Devil Stungun: In chapter 229, by using his arms, Sena is able to partially deflect Shin's Trident-Spear Tackle. His counter is likened to a foot soldier using the point of his sword to redirect the trident of a charging horseman away from him, rather than meeting the attack head on. The attack seems inspired by a similar move used against Agon Kongo of Shinryuji. Like a similar move used by Patrick "Panther" Spencer of the NASA Aliens, this move sacrifices ball safety for a chance to break through (Doburoku: "When you had twice the chance to break through your enemy, the chance of the ball being lost is 10 times greater"). Unlike the basic Stiff-Arm, this involves a jabbing motion. Used unsuccessfully against Marco of the Hakushuu Dinosaurs, who countered with the Screw Bite.
- Sagittarius: Inspired by the team strategy of the same name used by Shin and Sakuraba of Ojo, the Deimon version is first seen in the Hakushuu game. This combines the Devil Stungun and the Devil Backfire, and Sena becomes Monta's guard as the latter catches a pass. Monta refers to this as "Explosion MAX!"
Devil 4th Dimension : Sena's ultimate running technique, created during the Christmas Bowl against the Teikoku Alexanders. While running at his 4.2 second pace, Sena takes one quick backstep without changing his speed or stance: doing this during the instant of tackling causes the blocker to miss completely, rendering him off-guard while Sena cuts around. To the blocker, it seems as if time was running backward, hence the name (time being the "fourth dimension"). During the International Youth Cup semifinal match against Germany, Sena takes only a half-step back as a feint before he changed his run in order to defeat Germany's star player Schultz.
- Devil Bat 4th Dimension Ghost : The weakness of the Devil 4th Dimension is that for a moment after the backstop, there is a brief period of time where Sena lags: defensive players can take advantage by stopping their own movement while facing the backstep, going for the kill at exactly the right moment. Yamato chose to defeat the backstep by sealing it with his Caesar Charge, using his strength to increase his speed to super-light levels, completely overrunning Sena. Sena removes this weakness by combining the Devil 4th Dimension Run with the Devil Bat Ghost, confusing the blocker's perception at the moment of lag (since they are already committed to the tackle). Afterwards, Yamato mentioned that no amount of strength or talent could overcome this technique, for it is 'genuine speed'.
Trident Tackle: Shin's signature technique, which Sena used to try to tackle Panther in the world cup game against America. With Sena's weak arm strength, Panther easily shook him off.
Imagination: Not really an ability for play; Sena is frequently shown to have an excessive amount of imagination, whether he is on or off the field, while he's unconscious or fallen asleep. In his imagination, real or fictional characters appear, usually possessing extraordinary (and sometimes, absurd) abilities to teach, encourage, or push Sena forward in terms of mental strength.
- he imagines himself as a neat secretary (later discovered, similar to his father) who aids the team perfectly, right before deciding to be Deimon Devil Bats' secretary (1st Down)
- he imagines Deimon Devil Bat (Big) in his mind when trying to remember the TFP rule (12th Down)
- he imagines a 'Serious Eyeshield 21' comic character, who tells him not to run away and try to break through and past Mamoru Banba's defense (44th Down)
- he imagines Patrick "Panther" Spencer doing a moon jump wearing a space suit, where Cerberus pops Sena like a balloon to catch him (71st Down)
- he imagines the moment after defeating Agon Kongo, only to get stabbed by Seijuro Shin's Trident Tackleafterward, and eventually grilled up as food (205th Down)
- ...and much more
According to the Chapter 205 of the manga (205th Down: The Warrior's Sabbath Day), Sena's excessive imagination is passed on from his mother, Mihae Kobayakawa. Meanwhile, Sena's imagination of himself becoming a neat secretary is derived from his father, Shuuma Kobayakawa, who works as a lawyer.
- Sena is one of the more kind, caring, and determined members of the Devil Bats along with Kurita, Ishimaru, and Yukimitsu.
- Sena is one of the Deimon Shorties, other than Monta and Komusubi.
- Sena's entrance test number is 21, the same as his jersey number.