Natsuzora and RunSummer Sky and Run; 夏空エンド・ラン

From MangaHelpers: Second baseman Kaizu Chiaki is a normal senior high schooler who aims to reach the Koshien with his teammates and worries about his future career. One day, a new teacher arrives at his school. Her name is Takamine Touko. Crossing the boundaries between teacher and student, Chiaki and Touko find themselves gradually attracted to each other. [DrCoke]