Yokoi earned his D1 license through the Ikaten event and began competing in D1 Street Legal in 2007, driving a Nissan Silvia S15. He acquired the nickname "Zombie" after continuing to run his car following a wall strike during a practice and solo run session. He debuted in D1 Grand Prix proper and advanced to the Top 16 for the first time in the sixth round of the following season. In 2009 he claimed his first D1 Street Legal win in the final round, and three years later dominated D1SL with three wins across the season, taking the championship while also racing for D-MAX in D1GP.
From 2013, Yokoi began competing full time in D1GP. In 2014 he won his first D1GP round at Ebisu Circuit, defeating eventual season champion Kuniaki Takahashi, and finished third in the overall standings.
In 2015, Yokoi took a season in Formula Drift USA with backing from Yokohama Tires, picking up one win during his single campaign in the American series and earning the additional nickname "Galaxy Yokoi." He continued competing in D1GP simultaneously.
In 2016, Yokoi switched to a 2JZ-powered S15 built by his own shop. When Yokohama withdrew from D1GP in 2017, he and his team moved to Nankang tyres. He finished second in the 2017 D1GP standings with two wins, narrowly missing the title in the final round. That year he also competed in Formula Drift Japan and took part in the first FIA Intercontinental Drift Cup.
In 2018, Yokoi built a new S15 Silvia while his previous car was handed to teammate Akira Hirajima. Despite Masato Kawabata's dominance in the Solo Run competition, Yokoi secured three tandem wins and posted consistently high scores throughout the season. He clinched his first D1GP championship in the final round after Kawabata was eliminated in the Top 16.
In 2019, Yokoi won the first two rounds and collected two further podiums, maintaining the championship lead through the remaining rounds despite quieter outings, and claimed his second title — making him only the second driver after Youichi Imamura to win back-to-back D1GP championships.
The 2020 season saw him finish second in the overall standings while claiming the Solo Run championship. He was second again in 2021, with one round win. After two consecutive runner-up finishes, Yokoi won his third D1GP title in the final round of the 2022 season, equalling Masato Kawabata's tally and joining the small group of drivers with three or more D1GP championships.
In 2023, Yokoi's team switched tyre supplier to Goodride. He built a substantial points lead after winning the opening two rounds, but was disqualified from rounds three and four for tyre regulation violations, losing those points. Unable to recover his form — including two failures to qualify and a crash before a qualifying run at Autopolis — he ended the season eighth. In 2024, alongside new teammate and 2022 D1 Lights champion Yuki Tano, Yokoi switched to Toyo Tires under Tano's contract requirements. Without reaching a final all season, he finished fifth overall, the highest-placed Toyo-equipped driver.
At the 2025 Tokyo Auto Salon, Yokoi announced he would leave D-MAX at the end of the season after a 13-year association, while retaining the team as a sponsor. Competing alongside rookie and reigning D1 Lights champion Kenshiro Wada, Yokoi placed second in round two but could not maintain consistency, finishing the season fifth.
For 2026, Yokoi announced plans to compete under his own team banner, returning to an S14 Silvia platform — the same chassis type he drove at his D1GP debut in 2008 — powered by a 2JZ producing approximately 1,000 bhp. The car had been developed as a side project and previously campaigned at the World Time Attack Challenge in Sydney in 2024 and 2025.
Yokoi lives in Ichinomiya, Aichi, and runs MCR Factory — a shop he uses to build and maintain his D1GP cars. MCR stands for Mind Control Racing, the name of his street drifting team. The shop also fields a team in D1 Lights; in 2025, driver and employee Genki Mogami won the D1 Lights championship. Yokoi has two children and pursues jet skiing as a recreational interest.