Imanaga is a two-time NPB All-Star and he led the Central League in strikeouts in 2023 before signing with the Cubs during the 2023–24 offseason.

[2] Imanaga signed with the Canberra Cavalry of the Australian Baseball League to play weeks 2–7 of the 2018–19 Australian Baseball League season[3] In his six starts for the Cavalry, he posted a 4–0 win–loss record with a league-best 0.51 earned run average (ERA) over 35 innings pitched with 57 strikeouts to one walk.

By meeting the statistical recognition minimum (0.8IP per team game), Imanaga broke the league records for WHIP (0.429), H/9 (3.6), BB/9 (0.3) and second-best ERA behind Ryan Searle.

Following his ABL stint, Imanaga posted a 13–7 2.91 ERA, 2019 Nippon Professional Baseball season, finishing second in wins and strikeouts only behind Shun Yamaguchi in the Central League.

[6] On January 11, 2024, Imanaga signed a four-year, $53 million contract with the Chicago Cubs that also contained a fifth-year option.

[13][14] Imanaga played for the Japanese national team at the 2023 World Baseball Classic, and started the championship game in which Japan won 3–2.

"[24] When asked how he felt pitching in New York for the first time, Imanaga replied (through an interpreter) "The view from the hotel, I recognize it from Spider-Man.