After making his international junior debut at the 2017 edition of the Coupe du Printemps toward the end of the 2016–17 season, Tsuboi made his Junior Grand Prix debut the following autumn, placing fifth at both the 2017 JGP Belarus and 2017 JGP Italy. After winning the bronze medal at the 2017–18 Japan Junior Championships, he finished thirteen at the senior level. He returned to the Coupe du Printemps, this time winning gold.
