Ushijima made his international competitive karting debut in 2017 in the SKUSA SuperNationals for Phil Giebler Racing, competing against the likes of Jak Crawford and Zane Maloney.

In the 2019–20 MRF Challenge Formula 2000 Championship held during the winter in Dubai, Sakhir and Chennai, Ushijima logged two fastest laps and finished 7th in the standings.

For the 2020 season Ushijima signed with Hitech Grand Prix to race in the BRDC British Formula 3 Championship.

[9] Ushijima partook in post-season testing with Van Amersfoort Racing and was confirmed to drive for the team during the 2022 season, partnering Franco Colapinto and Rafael Villagómez.

[10][11][12] For his 2023 campaign, Ushijima left Formula 3 and signed to compete in the USF Pro 2000 Championship with Jay Howard Driver Development.