|Bats: left||Throws: right|
|Style||Aggressive batter and runner|
|Skills||80% on-base percentage
|Manga||Act II - Chapter 2|
Mima Souichirou is a student of Hakuryuu High School. He is the third batter and center fielder of the school's baseball team.
Mima is a lean built athlete with short, light colored hair.
Mima has a lot of confidence in his skills as a player and acts somewhat prideful about it. He thinks that Miyuki's reputation of being "the best catcher of his generation" has not been tested because he has not played against Hakuryu yet. In addition, he would often acts upon his own instinct when batting instead of following the direction or strategy of the team.
As his father was a former track and field athlete, Mima has a solid physical foundation as a sport player. He has a strong throwing arm, a speedy leg that can cover 50m in 5.8 seconds and sharp batting senses. He has recorded an on-base percentage of 0.8 and is touted as a prodigy batter that is receiving a lot of attention from pro-scouts.
When batting, Mima simply aims to return the ball and make a good hit instead of trying to bat to his team's advantage such as trying to pull the ball to a direction that would allow his on-base team mates more time to steal. In addition, Mima has sharp observation skill and was able to accurately identify Sawamura's Cutter the first time he sees the pitch while his teammates were still in confusion.
- Mima's father was a former track and field athlete and is currently working as a guest coach for Hakuryu High.
- Despite Mima impressive on-base percentage, he was not allowed on-base when facing against Komadai Fujimaki even when the Ace, Hongou Masamune, did not pitch that match.
- He has a habit of swinging his arm and pointing his bat towards the pitcher in a similar fashion to Ichiro Suzuki's at bat preparation. He usually tries to stay away from this as he's displeased with the fact people thinks he's mimicking Ichiro but will revert back to his habit unconsciously when he's concentrating hard.
- After the match between Hakuryuu and Seidou; Mima asked for Miyuki line account; however, Miyuki did not have a smart phone so the two kept in touch afterwards through messaging.
- "A base steal attempt can't be successfully prevented by the catcher alone. It's possible precisely due to the pitcher's cooperation. What an understanding kouhai you have here, so mindful of his catcher." - To miyuki (about Sawamura)
- Mima (美馬) - Beautiful Horse
- Souichirou (総一郎) - Complete/Total First Son