The Summer Regional Tournament are qualifying tournaments held in all 47 prefectures of Japan to determine the 49 teams that will compete at Summer Koshien each year. Teams are seeded base on how they perform in their Spring Regional Tournaments and Spring Prefectural Tournaments (i.e. Kanto Tournament).
In Tokyo's case, there are both West and East regionals. However, the Spring Tournament has teams from both regions face each other. If a team finishes in the Best 16 in the Tokyo Spring Tournament, they will automatically be a seeded team for their Summer Regional tournament.