Power Pro Kun Pocket 7

One day Hanamaru High School Baseball Club where main character belongs, is about to lose in a practice match when a mysterious hero "Red" appears from the electronic bulletin board, and match is won brilliantly. The next day "Red" comes as a transfer student. In addition, other heroes such as blue and yellow appeared, and the Hanamaru High School Baseball Club became a powerful team. But former members, including protagonist, are getting driven away from the main team. They need to take action to regain their robbed baseball club.

[From vndbreview]