Sasaki established himself as a dominant junior talent before entering the world stage. In 2015, he won the Asia Talent Cup and competed in the Red Bull MotoGP Rookies Cup, taking a race victory at Silverstone and finishing third in the standings. He returned to the Rookies Cup in 2016 and delivered a commanding campaign, winning four races, standing on the podium eleven times across thirteen rounds, and clinching the championship by 49 points. The title confirmed him as one of Japan's foremost emerging talents.
Sasaki made his Moto3 World Championship debut in 2016, appearing at the Malaysian Grand Prix as a replacement for the injured Enea Bastianini with Gresini Racing.
He became a full-time Moto3 competitor in 2017 with the Sepang Racing Team, partnering Adam Norrodin. Despite a strong rookie season that included top-ten finishes at Mugello and Phillip Island and the Rookie of the Year award, Sasaki struggled to break into consistent frontrunning form in his early years. Across 2017 and 2018 he scored 32 and 50 points respectively, each time finishing 20th in the standings.
Progress accelerated under Petronas Sepang Racing Team in 2019. Sasaki recorded five top-ten finishes, secured a pole position at the Sachsenring, and totalled 62 points. The 2020 season with Red Bull KTM Tech3 brought his first Moto3 podium — a second place at Aragón, reached by just 0.051 seconds — as he matched his new teammate Deniz Öncü across a tightly contested year.
In 2021, Sasaki opened the season with a string of top-five results and earned another podium with a third place at Aragón. That season was overshadowed by the tragic accident at the Italian Grand Prix in which fellow competitor Jason Dupasquier suffered fatal injuries following contact with Sasaki and Jeremy Alcoba. Sasaki withdrew from the next two rounds before returning to close the year with 120 points and ninth in the championship.
He spent 2022 with the Sterilgarda Husqvarna Max team and 2023 with Liqui Moly Husqvarna Intact GP. The 2023 campaign was his finest in the class: he finished runner-up in the championship standings, falling just short of Jaume Masià's title.
Sasaki made the step to Moto2 in 2024 with the Yamaha VR46 Master Camp Team, partnering Jeremy Alcoba — the same rider who had been involved in the 2021 Mugello accident. When the Yamaha VR46 Master Camp Team withdrew from the championship at the end of the season, Sasaki signed a two-year contract with RW-Idrofoglia Racing GP, competing under the Dutch RW Racing Team banner from 2025 onward.
Sasaki represents a generation of Japanese riders developed through the Red Bull and Honda Asia Talent Cup pathways who built lengthy careers in the intermediate world championship classes. His longevity in Moto3 — eight seasons encompassing every major team tier from satellite to factory-backed — and his eventual promotion to Moto2 reflect a patient, methodical development trajectory typical of riders who enter the Grand Prix paddock in their mid-teens.