The main character, Karin Kiritani, and her childhood friend, Rai Daimon, go to watch a women's professional baseball game. They come face to face with Satonishi and see firsthand the abilities of professional players. Then, they bumped into Mirei Hiiragi, who somehow ends up having tea with them! Finally, the summer tournament for the boys' baseball team begins. The boys' baseball team's first game is against Toranomon High School, the favorite to win the tournament. Will Rai be able to fulfill his promise to Karin. This volume is a renewed version of the previously released "Karin's Mound Volume 3" with a new side story.