The son of a fisherman, Iromi Itoh was born on August 31, 1997 in Shikabe, a town in southern Hokkaido. As a young boy, he got his introduction to baseball from Koki Morita, a former relief pitcher in the NPB who happened to be a childhood friend of his fathers and gave him personalized baseball instruction from a young age as a result. He grew up idolizing Hokkaido Nippon Ham Fighters ace Yu Darvish and focused on pitching as a result. He attended Tomakomai High School, the alma mater of Masahiro
Tanaka, but the school did not qualify for the Spring or Summer Koshien tournaments at any point while he attended.
After graduating in 2016, Itoh attended Komazawa University, but he dropped out after his first semester there, citing an inability to see himself remaining in school for another four years. After reevaluating his decision with friends and family, he enrolled at Tomakomai Komazawa University but because of college baseball rules, he could not participate in baseball games until a full calendar year passed between when he dropped out of Komazawa University. When he became eligible in his second year, he joined the Komazawa University baseball team and pitched for them for the remainder of his college career.
In October 2020, following his graduation, he was selected by the Hokkaido Nippon Ham Fighters, his local hometown club, with their first-round selection in the 2020 NPB Draft; he was actually the first first-round pick from Hokkaido to be selected by the Fighters since the team moved to the island from Tokyo. The 23-year-old right-hander agreed to terms with the team and made his professional debut a few months later, when the 2021 season began.
The rookie right-hander made his first professional start on March 31 against the Saitama Seibu Lions. He would go on to make 23 more in 2021 and would end the year posting a 2.90 ERA in 146.0 innings, allowing 125 hits, walking 53, and striking out 141. Though he certainly pitched well enough to deserve it, Itoh lost out on the Pacific League Rookie of the Year Award to Orix Buffaloes left-hander Hiroya Miyagi, who posted a 2.51 ERA in 147.0 innings, allowing 118 hits, walking 39, and striking out 131.
His 2022 began inauspiciously, as he contracted COVID-19, but he did not miss any time on the mound and ended up having an all-star season. Making 26 starts, Itoh posted a 2.95 ERA in 155.2 innings, allowing 140 hits, walking 49, and striking out 112.
Following the conclusion of the 2022 NPB season, he was selected to play with the Japanese National Team in an exhibition against Australia, and then a few months later, in the 2023 World Baseball Classic. The right-hander appeared in 3 games for Samurai Japan, all out of the bullpen, and was perfect, not allowing a single baserunner in 2.1 innings, striking out 3 batters. When he returned to Japan for the start of the 2024 season, he struggled and underperformed to the point that manager Tsuyoshi Shinjo considered having him removed from the starting rotation altogether. By May, he started turning things around, and while he ended up remaining in the Fighters rotation all season, it was a definite down year for the right-hander. He made 24 starts in total and posted a 3.46 ERA in 153.1 innings, allowing 147 hits, walking 41, and striking out 134.
Itoh recovered in 2024. He won a pair of Player of the Month Awards, one at the beginning of the season and one at the end, and posted a cumulative 2.65 ERA in 176.1 innings over 26 starts, allowing 150 hits, walking 39, and striking out 161. The Fighters made the postseason, going 75-60 and ending the year in second place in the Pacific League. They faced and beat the Chiba Lotte Marines in the best-of-three first stage of the Pacific League Climax Series, but lost against the league champion Fukuoka SoftBank Hawks in the best-of-six final stage of the Climax Series.
Itoh had been steadily improving, but everything came together for him in 2025. The 27-year-old appeared in 27 games and posted a 2.52 ERA in 196.2 innings, allowing 179 hits, walking 29, and striking out 195, his workload, BB/9 rate, and strikeout total all leading the league. The Fighters once again made the postseason, facing and beating the Orix Buffaloes, but as was the case in 2024, they once again lost to the SoftBank Hawks in the final stage of the Climax Series. While that would be the end of the line for the team, Itoh would still win one more thing. The right-hander won Eiji Sawamura Award by the award selection committee, meeting enough of their benchmarks for it to be awarded to him, unlike the 2024 season, when the committee determined that no single pitcher met enough of their qualifications and did not name an Eiji Sawamura Award as a result.
In spring, the 28-year-old right-hander participated in the 2026 World Baseball Classic. He appeared in two games for Samurai Japan and allowed 5 earned runs in 4.0 innings, allowing 4 hits, a pair of home runs, not walking a batter, and striking out 7. When he returned to Japan for the 2026 Fighters season, appeared in 26 games and posted a 3.18 ERA in 172.2 innings, allowing 184 hits, walking 34, and striking out 159.
The right-hander stands 5’9” and weighs 180-pounds, which is well below the average height for a pitcher (6’2”) and would make him the shortest starting pitcher in Major League Baseball. He would not be the shortest pitcher playing for a Major League Baseball club, as San Diego Padres reliever Yuki Matsui stands 5’8”. While there certainly may be some surface-level concern that his smaller frame might not be able to handle the rigors of the 162-game MLB season, Itoh has been an iron man in Japan, leading the league in innings pitched in 2025 and finding himself in the top 10 in innings pitched in five of the six years he has been pitching for the Fighters- and in 2021, the year he was not in the top 10, he was 11.
Itoh throws from a three-quarters arm slot, dropping and driving off the mound with a fairly small extension and a long arm action through the back. As many Japanese pitchers do, the right-hander features a hitch in his leg lift when the bases are empty, and wraps his wrist during the full extension of his arm circle. His delivery is smooth and balanced, allowing him to repeat his release point well and partially how he has maintained an extremely small walk rate throughout the course of his career.
Itoh’s arsenal of pitches is quite large, consisting of a four-seam fastball, two-seam fastball, cutter, splitter, slider, curveball, and changeup. In 2026, he threw his four-seam fastball 36.6% of the time, his slider 23.7% of the time, his splitter 13.4% of the time, his two-seam fastball 10.4% of the time, his cutter 6.2% of the time, his curveball 5.5% of the time, and his changeup 4.2 of the time. Going back to 2024, he used his cutter and splitter a bit more, but his pitch usage has otherwise broadly remained consistent over the last few seasons. All in all, Itoh is most effective in the shadow of the zone, getting batters to get themselves out by confusing them with his wide assortment of pitches that he is able to spot all over the strike zone.
Itoh’s four-seam fastball averaged 92 MPH in 2026, topping out at 94 MPH. It features above-average arm-side movement and regularly posted above-average 15”+ induced vertical break readings, making it most effective in the upper quadrants of the strike zone. Itoh’s two-seam fastball has similar characteristics, exchanging some velocity for additional arm-side movement.
His slider averaged 83 MPH in 2026, and when the pitch is at its best, it features sharp sweeping horizontal movement in addition to hard vertical break. Itoh either does not always get a good horizontal tilt on the pitch or liberally mixes in a harder gyro slider that minimizes horizontal movement. In 2026, his slider was actually an ineffective pitch, with a slightly negative weighted runs above average per 100, but in 2025 and prior seasons, the pitch was slightly positive.
His splitter averaged 87 MPH in 2026. The pitch tunnels well with his fastball and features late downward drop. Like his slider, the pitch resulted in a slightly negative weighted runs above average per 100, but in past seasons has fluctuated between being slightly above-average and slightly below-average.
His cutter is thrown hard, averaging 90 MPH last season. Last season, it resulted in the highest weighted runs above average per 100 of all of his pitches and has consistently been one of Itoh’s most effective offerings thanks to its combination of velocity and late darting movement.
Itoh’s curveball averaged 76 MPH last season. The big bender features loopy 12-6 drop and is more of a change-of-pace offering than a real swing-and-miss pitch due to its lack of bite. His changeup, which averaged 84 MPH, is similar. Because it lacks dynamic fade or tumble, the pitch is more of a strike stealer or set up to begin a sequence rather than an effective pitch in and of itself.
On the whole, Itoh does a good job of keeping the ball in the stadium, posting a 22.3% line drive rate, 41.0% groundball rate, and 36.8% flyball rate in 2026, with slight variations in those trends over the course of his career. In particular, his sinker, splitter, and changeup have been effective worm killers.
All in all, nothing in particular stands out as being decidedly above-average in pitching repertoire, but the right-hander has a high amount of pitchability. He knows when to throw what pitches, all of his offerings have synergy with each other, and he is able able to command them all.
Itoh has the nickname “Mr. White Smoke” stemming from an incident that took place during the 2021 Summer Olympics. Members of the South Korean National Team complained that the amount of rosin that Itoh was using was distracting, and that he was intentionally using so much powder in order to confuse hitters by leaving a lingering cloud of rosin in the air around the mound. Itoh’s response was that he was not intentionally trying to gain an advantage over hitters by making it harder for them to see, but that he simply is a sweaty individual.
