For those wondering why he is so agile, he has been playing second fiddle to protagonist-like people his entire life. I think at some point it's mentioned he was the best friend of some Captain Tsubasa's ripoff and helped him turn his team into an elite one (I think he was the second best player too). He also has other talents from similar situations but he doesn't use them that much.
Dude basically has crazy potential (I mean, he is THE protagonist after all) but kind of squanders it because he is obsessed with being a mob-like character.
EDIT: I just noticed this is literally shown in the first chapter. I thought they had skipped it. So yeah, there you have it.