|Seidou High School - No. 20|
|Bats: Left||Throws: Right|
|Education||1st Year High School|
|Manga||Act II - Chapter 1|
|“||You are a tough one!||”|
— Sawamura to Yui
Yui is a short boy with light brown hair, thick eyebrows, big eyes, and is often seen wearing a smirk on his face.
Yui is a confident teenager having a very competitive spirit. He hates to lose specially to his similarly competitive teammates whether it be at running laps, batting or simply eating meals.
He was the unshakable starting catcher in the Mamiya Senior League, and is a known prodigy in his generation who captained the Japanese Representative team in the Little League World Series.
Arriving early at Seidou, Yui has a brief encounter with Okumura, Seto and Yuuki after which, he heads to the dorms. In the dorm room, he tells Furuya to feel free to call him anytime Furuya feels like pitching for he is a catcher and admits that he's been interested in seeing Furuya's pitches for the longest time.
Yui watches Seidou's third round match against Eigen from the bleachers. He makes it to the first string and observes how Miyuki leads Furuya in the fourth round. Later at the Seidou dorm, Sawamura asks Miyuki to catch for him but Yui is quick to volunteer instead as he found it difficult to catch Sawamura's pitches in the bullpen.
After Seidou's quarterfinals match victory, Yui offers to catch for Furuya knowing that Furuya isn't satisfied pitching in the quarterfinals. Furuya declines Yui, prefering to have Miyuki catch for him instead, to Yui's surprise. Furuya says that he wants to pitch at ease without holding back. Yui then feels frustrated, clenching his fists while thinking back during practice that he's had a hard time catching Furuya's pitches.
Relationship with other charactersEdit
He highly respects the ace of the team, who is also his roommate and eagerly wants to catch for him, because he's interested in seeing Furuya's pitches up close.
He is also interested in Sawamura's pitches and wants to catch for him as soon as an opportunity arises because he had troubles catching his pitches the first time.
Yui has power, good running, and an excellent shoulder.
- Yui is one of the few freshmen who can easily scarf down breakfast and is always first.
- Yui (由井) - Well of Reason
- Kaoru (薫) - Fragrant
- "If they are serious about the national championship, they'll need this pitcher." - about Sawamura
- "I can't help wondering just what kind of fastball he throws." - about Sawamura 
|Seidou High School|
|Miyuki Kazuya • Maezono Kenta • Kuramochi Yōichi • Kawakami Norifumi • Asou Takeru • Nakata Ataru • Ono Hiroshi • Higasa Shōji • Seki Naomichi • Yamaguchi Ken • Kijima Rei • Kawashima Kengo • Shirasu Kenjirō • Mimura Ryōta • Watanabe Hisashi|
|Sawamura Eijun• Furuya Satoru • Kominato Haruichi• Kanemaru Shinji • Tōjō Hideaki • Kaneda Tadahiro|
|Yui Kaoru• Yūki Masashi • Okumura Kōshū• Mogami Takeshi • Asada Hirofumi • Seto Takuma • Kuki Yōhei
|Former players||Yūki Tetsuya • Tanba Kōichirō• Kominato Ryōsuke• Masuko Tōru• Isashiki Jun • Miyauchi Keisuke • Sakai Ichirō • Kadota Masaaki • Kusunoki Fumiya • Takigawa Chris Yū • Azuma Kiyokuni
|Managers||Fujiwara Takako • Umemoto Sachiko• Natsukawa Yui• Yoshikawa Haruno
|Staff||Kataoka Tesshin • Ochiai Hiromitsu • Takashima Rei • Kazuyoshi Oota|