Whistle! is based on a popular manga under the same title published on weekly "Boy Jump" by Daisuke Higuchi. It was made into anime to celebrate 2002 FIFA World Cup which will be co-hosted by Japan and Korea.
The story focuses on Sho Kazamatsuri, one of the best junior highschool soccer player. The theme of the anime is youth, friendship, a hero who try hard without giving up his dream to be the best soccer player and his team mates.
There are 30 seconds of soccer mini lesson on every episode to introduce the foundation of soccers such as how to kick a ball.