Ace of Diamond OVA

Eijun Sawamura, the pitcher of a novice junior high baseball team, meets with a bitter walk-off loss. For Sawamura the loss becomes his last game in junior high, so he sets a new goal of going to the nationals in high school with his teammates. As he begins his hard quest on studying, a guest arrives unannounced. Her name is Rei Takashima. Rei had been watching his last game and believes Sawamura has a gift. She is the assistant director of the prestigious Seidou High School Baseball Team, and she invites Sawamura to Seido after seeing his potential. Sawamura's reply shocks her, but Takashima refuses to give up and tricks Sawamura into a visit.

Kazuya Miyuki becomes the catcher for Sawamura in a contest against Seido's dangerous clean-up batter, Kiyokuni Azuma. As Eijun tries to pitch down the middle, he finds himself tense and unable to control the ball. Kazuya immediately calls time and comes out to give him some words of encouragement. The words have the desired effect as Eijun finds more control than ever before and unveils a dangerous weapon he didn't know he had. Seeing how people like Kazuya can alter his pitching, Eijun decides to come to Seido as long as he can become the ace of the team.

Eijun is nervous about rooming with older teammates, but they make him feel a too little at home on his first night. Eijun ends up oversleeping and shows up late when it's time to meet Coach Tesshina Katoka, a former Japanese pro pitcher. Miyuki also shows up late, but he uses Sawamura as a decoy to sneak into his line. Katoka shows no mercy and says Eijun can never become a pitcher if he can't show up on time. He also makes Miyuki run laps. Sawamura is determined to prove he can be the ace though, so Coach Katoka gives him a special challenge, saying until he can complete this challenge, he can't play in a baseball game for Seidou.