Eyeshield 21 is a coming-of-age sports manga written by Riichirou Inagaki and illustrated by Yuusuke Murata. It ran in Weekly Shounen Jump from 2002 until 2009, and its 333 chapters were collected into a total of 37 volumes.

The story centers on Sena Kobayakawa, a short, timid first-year student at Deimon High School who spent most of his childhood running from and gofering for bullies. Thanks to this, Sena developed superhuman speed and agility, a talent that Youichi Hiruma—Deimon High's maniacal shadow tyrant and cunning quarterback—quickly discovered. Hiruma forcibly drafts Sena as the new running back for his struggling American football team, the Deimon Devil Bats. Sena also has to wear a tinted visor helmet and use the codename "Eyeshield 21" during games, so that other sports clubs don't uncover his identity and recruit him.

Throughout the series, Sena gains new teammates as they overcome numerous obstacles in the tough world of American football, all with their eyes on Japan's high school national championship, the Christmas Bowl. As he faces down new rivals and difficult plays with each new game, he grows into a braver person and a stronger athlete who learns to love the sport.

Seijuurou Shin is Sena's first-ever rival, and the one that motivates him to keep playing American football out of his own personal desire. Sena is also the first player to ever outrun Shin, which earns him Shin's respect early on, both as a fellow athlete and worthy opponent. Even as Sena meets and plays against more rivals, Shin is the one he looks up to the most, and the feeling is mutual. Through the duration of the series, both of them are motivated by one another to improve their strength and speed, with the promise of one day facing off against each other again.

Additionally, the two of them function as foils of each other, both physically and in terms of personality. Shin is taller and far more muscular than Sena, a stoic who's laser-focused on improving his physique. Meanwhile, Sena's build is much shorter and more trim, with a bashful and nervous disposition to match. Neither of them have the best social skills, which can make their interactions humourously awkward, not that this deters their mutual admiration.