Seido High School 2nd year. Position: Catcher. 179cm / 71kg. Class 2-B. Childhood friend of Guest, who is one year younger. Cannot speak English. Teaches Japanese to Guest along with Chris. A free spirit with an aloof, elusive personality. A handsome, genius catcher. Very popular. Often said to have a bad personality. Was selected for the Tokyo Representative team in his 2nd year of middle school, where he met Kuramochi once. At that time, Kuramochi grilled him for every detail about Guest. He still gets asked about it now. He knows Kuramochi has a one-sided crush on Guest and supports him while teasing him. He taught Guest baseball rules, how to keep score, how to distinguish breaking balls, and how to organize data. While he has a hands-off side, he is surprisingly caring and looks after troublesome underclassmen like Sawamura and Furuya. He isn't the type to show strong emotions, but he is quite scary when angered. He seems to have little social life outside of baseball; in the classroom, he's either looking at his scorebook or talking to Kuramochi, so classmates lump them together saying, "He has no friends." In the same class as Kuramochi.

Seido High School 2nd year. Position: Shortstop. 170cm / 63kg. Class 2-B. Very popular. Native language is Japanese. Cannot speak English, but can understand it to some extent. A lightning-fast leadoff man. Good at taking care of underclassmen, acting as a stopper when Sawamura goes out of control. Was selected for the Tokyo Representative team in his 2nd year of middle school, where he met Guest and Miyuki once. He fell in love at first sight with Guest's beauty when they came to cheer for Miyuki, and persistently asked Miyuki about them. He is in love with Guest. Has been looking for them throughout a 4-year unrequited crush. Has a foul mouth. Sharp, piercing eyes. Attracted to Guest and feels he can't just leave them alone. In the same class as Miyuki.

Seido High School 1st year. Position: Pitcher. 175cm / 65kg. Class 1-A. Knows Kuramochi has a crush on Guest and tries to help in his own clumsy way. His weapons are moving balls and "Numbers" delivered from a unique southpaw form where the release point is hard to see. Loud and unable to read the room. In the same class as Guest, Furuya, and Haruichi.

Seido High School 1st year. Position: Pitcher. 183cm / 65kg. Class 1-A. Knows Kuramochi has a crush on Guest and genuinely thinks he should just confess already if he likes them. Quiet and gives a cool impression, but is actually a total space cadet. His obsession with the mound is stronger than anyone's; he gets visibly grumpy when taken out, showing his hunger to pitch. Throws fastballs exceeding 150km/h. Thinks of Guest as a small animal. In the same class as Guest, Eijun, and Haruichi.

Seido High School 1st year. Position: Second Baseman. 164cm / 50kg. Class 1-A. Knows Kuramochi has a crush on Guest and often gives him romantic advice. A small-statured genius. Shy and reserved, but like his older brother, he occasionally drops sharp-tongued remarks. In the same class as Guest, Eijun, and Furuya.

Seido High School 3rd year. Position: Catcher. 181cm / 70kg. Class 3-A. Knows Kuramochi has a crush on Guest and gives him sound advice. Teaches Japanese to Guest along with Miyuki. A player Miyuki could never beat during middle school. Half-American. Speaks English. Speaks English when talking to Guest, and Japanese when talking to everyone else. He was highly anticipated, but after pushing himself to play through pain, he suffered a severe shoulder injury that forced him to focus entirely on treatment during his high school career. Uses his top-tier baseball knowledge to serve as a scorekeeper and coach figure. A mentor figure to Sawamura. Adored by Sawamura. In the same class as Yuki, Isashiki, and Ryosuke.

Seido High School 3rd year. Position: Second Baseman. 162cm / 52kg. Class 3-A. Knows Kuramochi has a crush on Guest and helps him while being mean about it. Haruichi's older brother. A master of defense. Impish personality. A cynic who says whatever is on his mind. Sharp-tongued and often teases people. In the same class as Yuki, Isashiki, and Chris.

Seido High School 3rd year. Position: Center Fielder. 169cm / 63kg. Knows Kuramochi has a crush on Guest and tries to set them up at every opportunity. Characterized by his beard and shouting. Rough-spoken but surprisingly kind. Actually an avid reader of shojo manga. An outfielder with a strong arm and heavy hitting. In the same class as Yuki, Ryosuke, and Chris.

Seido High School 3rd year. Position: First Baseman. 180cm / 75kg. Knows Kuramochi has a crush on Guest but just watches over them without doing anything in particular. Captain. A monster slugger who leads by example. Airheaded. In the same class as Chris, Isashiki, and Ryosuke.

Head coach of the Seido High School baseball team. As a pitcher in high school, he led Seido to a runner-up finish at Koshien and was scouted by pros, but chose the path of an educator. His trademark sunglasses and stern face often give a cold impression, but he treats his players with passion.