Yūichirō Tajima (田島 悠一郎 Tajima Yūichirō) is Nishiura High School's baseball team's third baseman, as well as former cleanup hitter and reserve catcher. His spot as the cleanup hitter was given to Hanai during Nishiura's game with Senda High School.
Tajima is considered to be a baseball prodigy. He mentioned that he hasn't ever seen a pitch that he could not hit by the end of the game. During the summer tournament, Tajima showed his attention to detail and baseball prowess as a first base coach when reading Tosei's pitcher in order to help runners steal second base. He has a strong throwing arm and good reflexes. He used to be the clean-up hitter for Arakawa Sea Breams, which gathered players from all over Kantō, but due to his small build, he cannot hit home runs.
Tajima mentioned that he decided to enter Nishiura because it is close to his house and his grandfather's garden. During middle school, his great-grandfather had to go to the hospital, but because no one informed him, he had spent the night at home alone, worrying (with all of his pets), while the rest of his family had been at the hospital and then went out to eat dinner, completely forgetting about him. Now in high school, if in case his great-grandfather or his grandparents ever go to the hospital, he would know immediately and not be left behind again.
Tajima has short black hair that is styled in spikes, brown eyes, and a fairly tan complexion. Like all the characters in the series, he has a natural pink blush under his eyes. At the start of the second season, his hair is noticeably shorter. Small in stature, Tajima is below average height for his age, he is only one centimeter taller than Momoe, and stands at 5'4". His most prominent facial feature is his row of freckles along the bridge of his nose. Jovial in nature, his expressions are usually of him smiling.
Tajima is an outgoing person and can thus make up for Mihashi's shy nature. Mihashi and Tajima have been shown to get along well as they share their love of baseball and bad school grades. He is one of the few people Mihashi feels comfortable with arguing and yelling at.
Tajima has a natural shameless personality, able to both strip and talk about masturbation in public. Hanai and Izumi often yell at him or hit him to make him stop, and even then he simply prattles on as if talking about those sensitive subjects were the most natural thing in the world.
Tajima gets on well with the rest of his teammates, particularly Mihashi, where he seems to understand him even when Mihashi can only stutter a few words, sometimes even by fidget. Tajima often acts like a big brother to Mihashi, protecting him and getting angry if he thinks Mihashi is being bullied. It is also shown that Mihashi would hang out with Tajima often enough that his grandfather and the rest of his family (including Tajima) would call Mihashi by his first name, Ren, and Mihashi would do the same for Tajima, calling him "Yū-kun".
Hanai is seen having an inferiority complex toward Tajima, as he is always the 'second', Tajima beating him in all but height and ability to hit a homer. Their relationship is odd if anything, as they cheer for each other as teammates should, but have a rivalry going inbetween. In the latest chapters, it is noticed that Tajima has insecurities too, when Hanai is given the cleanup spot in the game against Senda, and later on, more of them add up as Hanai hits a homerun during batting practice, which Tajima cannot do even during games, due to his physique.
Abe is seen envious of Tajima since he can understand Mihashi way better and manage to comprehend what the other is saying even by just a few words or movements, whilst Abe cannot understand unless told clearly and properly. Tajima is starting to feel rivalry on Abe for the catcher position after a while as well.
- (To Hanai) "You got two runs. Let's make the next inning the last."
- The name Yūichirō means "permanence" (悠) (yū), "one" (一) (ichi) and "son" (郎) (rō).
- Yūichirō's surname Tajima means "field, rice paddy" (田) (ta) and "island" (島) (shima/jima).
- Tajima is the shortest among his teammates.
- Tajima only takes 1 minute to go to school since he lives nearby, but he takes a lot of time to return since he usually goes to Ren Mihashi's place.
- In spite of his bad school grades, Tajima can recite the scores of a baseball game after he saw or heard it once.
- Tajima prefers girls with short hair or the ones that wear it tied up. He finds Chiyo Shino'oka cute and mentioned that if Maria Momoe was a 15-year-old girl, he would totally like her.