The following season, he made his full-time debut in the 2019 championship with backing from the Honda Formula Dream Project,[1] claiming 2 wins but finishing 6th in the standings.

That year, Ohta also made a guest appearance in the French F4 championship alongside Honda stablemate Ren Satō, where he finished in the top ten in the three races he competed in and secured one podium.

He would also make an appearance in Japan Formula 4 at the end of the year, winning the "All-Japan Deciding Race" over the likes of Satō, Atsushi Miyake, and Riki Ōkusa.

[7] However, he was chased down by teammate Makino in the closing stages and lost the victory on the penultimate lap, as a throttle issue caused him to spin out of the race.

[8] Ohta had another strong qualifying session in Fuji, as he started from second, but dropped to ninth by the flag due to degrading tyres in the final laps.

[13] On December 11, 2024, it was announced that he would be driving 3 races during the 2025 IMSA SportsCar Championship in the 93 Acura Meyer Shank Racing Acura ARX-06, alongside Renger van Der Zande and Nick Yelloly, for the Rolex 24 Hours at Daytona, Six Hours of the Glen at Watkins Glen and the Battle of the Bricks at Indianapolis Motor Speedway, and Alex Palou for the Rolex 24 exclusively.