Saito grew up with a strong interest in motorbikes, a hobby passed on by his father, and obtained his motorcycle license at 16. His introduction to drifting came one evening when, riding in the hills of Karuizawa with friends, he came across a car meet where a white Mercedes-Benz saloon was being drifted. The sight redirected his ambitions entirely. When he turned 18 and acquired a driver's license, his father bought him a Mini Cooper, a car ill-suited to drifting, which Saito wrote off attempting to drift anyway. He then bought a Nissan Silvia S13 and began practising immediately, reportedly spending 36 consecutive hours in his first practice session. That car was also crashed within weeks, but the pattern of total commitment was set.
Saito began competing in the D1 Grand Prix in the third round of the 2004 season, driving a Toyota Mark II JZX90. He improved steadily and won his first D1GP championship in 2008. In 2011 he became the series' first-ever Tanso (Solo Run) champion, driving a Toyota JZX100 Chaser.
After a period split between D1GP and Formula Drift, Saito returned to full D1GP focus in 2015, finishing as runner-up with three event victories while driving the first drift-specification Lamborghini Murcielago. In 2016 he won five rounds in a single season — a record later equalled but not surpassed — and clinched his second D1GP title with a round to spare. That five-win season also produced his second Tanso championship.
Later D1GP campaigns saw Saito campaign a Chevrolet C6 Corvette in 2017, then transition to a Toyota GR Supra from 2019 onward. In 2022 he also competed in Formula Drift Japan alongside teammate Hokuto Matsuyama in identical Toyota GR86 machinery before the team was disbanded at year's end.
Saito entered Formula Drift in 2012 driving an Achilles Radial Lexus SC430 powered by a Toyota 2JZ engine, maintained and transported by Bridges Racing. His debut season was extraordinary: he won at Palm Beach, took additional podiums at Long Beach and Atlanta, and clinched the championship with a win at Irwindale in Round 7. He was also named Rookie of the Year. No driver had previously won the Formula Drift championship in their debut season.
In 2013 his second Formula Drift season brought three round victories — at Atlanta, New Jersey, and Irwindale — and a second-place finish at West Palm Beach, though a practice crash at Seattle and mechanical issues in Texas effectively ended his title defence. He finished third overall.
For 2015 Saito debuted a 1,200 horsepower Nissan GT-R built in partnership with HKS, campaigning it through the season. He returned to Formula Drift competition in subsequent years before eventually withdrawing from the US series to focus on D1GP.
Saito's arrival in Formula Drift in 2012 was credited with a fundamental shift in the series. American commentators coined the term "the Daigo effect" to describe the significant increase in horsepower across the field and the change in tandem judging criteria that followed his debut. His high-power, high-angle style raised competitive expectations in ways that reshaped how other teams built and drove their cars.
Outside the major drift series, Saito won the rear-wheel drive class at Gymkhana Grid in 2018 and competed in the Russian Drift Series that year, finishing as runner-up. His 2010 video "Battle Drift," produced by Monster Energy and filmed at an abandoned Russian village in Niigata alongside Vaughn Gittin Jr., attracted over 40 million views and significantly raised his international profile.
As the only driver to win both the D1 Grand Prix and Formula Drift championships, Saito occupies a singular position in the history of professional drifting. His five D1GP wins in a single season, his three consecutive Formula Drift Asia championships from 2011 to 2013, and his two D1GP Tanso titles add further depth to a career that stretched across two continents and multiple vehicle platforms over two decades.