Eyeshield 21 (2005-) 
Kobayakawa Sena is a little guy who always get picked on by the bullies in school. Since elementary school, he always play the role of the 'errand boy' to the extent that he has become ...
Eyeshield 21: "The Man with the Lightspeed Legs!" Season 1, Episode 1
We are introduced to Sena and Mamori! Best friends where a romantic intersection is kinda unthinkable. I mean, it hurts just to think about it. And that's where the genius in this starts.
o yeah this is a sports anime about highschool American Grid Iron Football in Tokyo played between public and private schools [more inside]