This article says following;
The high school baseball players have missed this year's games at Koshien Stadium because of COVID-19. The game is the championship of high school baseball. Many famous Japanese professionals have played on the field there. Every year, the players gather a handful of dirt from the field to take back home after finishing their games. But, this year, the dirt will be sent to the players by Hanshin Tigers, which is a professional baseball team based on Koshien Stadium.
This article says Koshien is located Hyogo state. We officially call it Hyogo prefecture.