The Interhigh championship is a high school basketball tournament in Japan. It is hosted every year and is held in every region, to look for the best teams of that region to advance to the Nationals. In Kuroko no Basuke, only the Interhigh, Tokyo region has been seen.
Before the actual Interhigh, there are preliminaries first. They are held in four separate blocks, Block A to D. The teams must advance 5 rounds, the semi-final and the final to be the winner of their block. That team is qualified for the final league of the preliminaries. In that final league, those four teams compete against each other and the best three teams will finally advance to the Interhigh.
The best eight of every prefecture, so the winner and runner-up of every block, are qualified for the Winter Cup preliminaries. Teams that couldn't belong to these two teams cannot compete, for example Seihō High.