Koki Saito was born on 10 August 2001 in Kanagawa and made his J2 League debut for Yokohama FC as a teenager. Even before turning 19 he had moved abroad — joining Belgian second-tier club Lommel United in January 2020, where he scored 5 goals in 20 Challenger Pro League matches in his debut season.
Saito then moved to the Eredivisie with Sparta Rotterdam in 2022, where he had two productive seasons: 30 league matches with 7 goals and 5 assists in 2022–23, then 22 league matches with 3 goals and 5 assists in 2023–24. After a brief return to Lommel and a loan move to QPR in the English Championship in August 2024, he made the QPR move permanent in summer 2025.
His Championship years have shown his ability to compete in a physical, possession-disrupting league: 39 league matches with 3 goals and 2 assists in 2024–25, then 34 matches with 3 goals and 2 assists in 2025–26. He represented Japan U-23 at the Paris 2024 Olympics and earned his senior Japan A-team debut in 2025.
A 170cm two-footed left-sided attacker with excellent close control, change of direction and the work rate to defend, Saito has carved out a unique career path through Belgium, the Netherlands and now England. He is a natural fit for Japan's wide attacking rotation as the squad considers depth options heading into the 2026 FIFA World Cup.