"Eyeshield 21" is traditional sports anime about a kid who learns to believe in himself and become a winner, but at the same time it is also a comedy with a bizarre twist - it's about a group of misfit Japanese high school kids forming a team to play "American Football" in their Japanese high school. So you not only have all of the usual "Gambatte! Gambarimasu!" (Do your best! I'll do my best!") sort of stuff, but also an attempt to give a Japanese youth audience a crash course in American-style football. The result is a spectacularly funny comedy, both deliberately - due to the wacky cast of misfits - and also unintentionally, because of the ongoing attempts to explain the rules and concepts of American football during the eyecatches and off-and-on during the story line.
First year high school student Sena has always relied upon his older female friend Mamori to protect him. And when Mamori isn't around, Sena has learned to run away from trouble because he is smaller than most of the bullies that bother him. But now that Sena is in high school he no longer wants to be "protected by a girl" and allows himself to be talked into joining his high school's American Football team, which has few players, never wins, and is almost unknown in the high school. But Sena's "running away" has developed him into a phenomenon - he can out run most pursuers and thread his way through most obstacles, including football defensive teams. Because of that, the fanatical and demonic captain of the football team, Hiruma, decides to rebuild the team around Sena, with Sena disguised as the mysterious running back "Eyeshield 21".
What results from this is a fast-paced, unpretentious story with surprisingly adept character development and smart, consistent comedy. Add to this reasonably good animation and a lively soundtrack and you have a nice bit of old-fashioned fun done in a thoroughly up-to-date manner. So forget about anything you ever knew about American High School Football, sit back, grab a bottle of "sports water", and enjoy the action.