Complex sentence: The series tells the story of Sena Kobayakawa, a introverted boy who joins an American football club as secretary, but after being coerced by Hiruma, turns out to play wearing an eyeshield and the number 21, under the pseudonym of "Eyeshield 21".
Split into simpler sentences: The series tells the story of Sena Kobayakawa, a introvert boy who joined the American football club. He initially joined the club as secretary, but after being coerced by Hiruma, turns out to play wearing an eyeshield and the number 21, under the pseudonym of "Eyeshield 21".