The Interhigh championship is a high school basketball tournament in Japan. It is hosted every year to decide the best highschool basketball team. Each team must first become one of the three best of their region before advancing to the actual IH, where they compete against teams from other regions.
Before the actual Interhigh, there are preliminaries first. These preliminaries are divided into regional tournaments, for example the Kantō tournament (where Tokyo is situated). Each tournament is separated into 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 of that region 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.