Chitose is a high school baseball player who had to abandon baseball due to injury. One day, when Chitose was spending a boring day off without any goal, Chitose's life changed completely with a "VRMMO game" that was suddenly sent by his sister Haruka! "Oy Onii-chan, let's play a game together in our spare time!" A high school baseball player became a gamer at the invitation of his cute sister!? Using his "excellent baseball sense" to enjoy a fun game in a VR world!