2021: two-year-old season

Do Deuce began his racing career in a contest for previously unraced juveniles over 1800 metres on good to firm ground at Kokura Racecourse on 5 September 2021. Ridden by Yutaka Take he started the 0.7/1 favourite and won by a neck from Gaia Force. Take was again in the saddle when the colt was stepped up in class to contest the Listed Ivy Stakes over the same distance at Tokyo Racecourse in the following month. He started second choice in the betting and prevailed by a neck and three quarters of a length from Gran Cielo and Ask Victor More after taking the lead in the straight.^[7]

On 19 December at Hanshin Racecourse, Do Deuce was stepped up to Grade 1 class to contest Asahi Hai Futurity Stakes over 1600 metres and went off the 6.8/1 third choice in the betting behind Serifos (winner of the Niigata Nisai Stakes) and Geoglyph (Sapporo Nisai Stakes). Take positioned the colt on the outside in mid-division before producing a strong run down the centre of the straight. He got the better of a sustained struggle with Serifos in the last 200 metres to win by half a length. After the race Take, who was winning the race for the first time, said “Do Deuce is an honest colt. We were able to run in a good position and in good rhythm while observing the others. He responded well going into the straight and although the favorite was stubborn and hard to beat, he dug in remarkably all the way to the line. He’s getting stronger by every race—we can look forward to the spring classics next year."^[8]

In January 2021, at the JRA Awards, Do Deuce was named Best Two-Year-Old Colt, taking 251 of the 296 votes.^[9] In the official Japanese rankings Do Deuce was rated the best two-year-old of 2021, one pound ahead of Serifos and the Hopeful Stakes winner Killer Ability.^[10]

2022: three-year-old season

On his first run as a three-year-old, Do Deuce started favourite for the Grade 2 Yayoi Sho over 2000 metres at Nakayama Racecourse on 6 March. He tracked the leaders for most of the way and finished strongly but sustained his first defeat as he failed to run down Ask Victor More and was beaten a neck into second place. In the Satsuki Sho over the same course and distance on 17 April the colt started the 2.9/1 favourite in an eighteen-runner field but despite producing a strong late charge from the rear of the field he was unable to reel in the leaders and came home third behind Geoglyph and Equinox.^[11]

On 29 May Do Deuce was one of eighteen three-year-olds to contest the 85th running of the Tokyo Yushun over 2400 metres at Tokyo Racecourse, and, with Take again in the saddle went off the 3.2/1 third choice in the betting behind Danon Beluga and Equinox. The other contenders included Geoglyph, Ask Victor More, Justin Palace, Killer Ability, Matenro Leo (Kisaragi Sho) and Ask Wild More (Kyoto Shimbun Hai). After racing towards the rear of the field he began to make progress and moved up into contention on the wide outside on the final turn. He made relentless progress in the straight, overhauled the leader Ask Victor More 150 metres from the finish and held off the late challenge of Equinox to win by a neck. Yutaka Take, who was winning the race for the sixth time said "This is a truly emotional experience for me... Though my colt isn’t such a good starter, we were able to sit in an ideal position so the fast pace didn’t bother me. He had so much left in the tank at the final corner when I asked him for his run—he responded amazingly and took the lead earlier than planned but held on well."^[12]

Do Deuce then went to France to run in the Prix Niel before running in the Prix de l'Arc de Triomphe. He finished fourth to Simca Mille for the Prix Niel and finished 19th against Alpinista for the l'Arc de Triomphe, which was the worst out of the four Japanese horses that ran that year.^[13][14][15]

After returning to Japan, it was announced that he would take the remainder of the year off before returning to the races at next year's Kyoto Kinen, with the Dubai Turf in mind.^[16][17]

2023: four-year-old season

Do Deuce became the first Derby winner in 75 years to win the Kyoto Kinen, after he became the most favored to win.^[18][19][20] However, he was ultimately scratched from the Dubai Turf due to his near-fore being lame during a pre-race medical check.^[21]

He would not return to racing until October 29 when he was entered in to the Autumn Tenno Sho to face Equinox once again. However, Do Deuce finished at 7th in that race, with his usual jockey being injured as a result of being kicked by another horse that day and instead ridden by Keita Tosaki [ja], who was a last minute replacement.^[22][23] Tosaki would reprise his role as Do Deuce's jockey in the following Japan Cup, as Take was still recovering from his injuries at the time,^[24] but finished fourth behind Equinox.^[25]

Take returned to race with Do Deuce for the Arima Kinen, held on December 24, where he was the second favorite. At the race, the horse managed to run past the pack at the final corner, overtaking the likes of Stars on Earth and Titleholder, winning his third Grade I race with a half length lead.^[26][27] After the Arima Kinen; Take, Tomomichi, and Matsushima (head of Kieffers) expressed their desires to return to Dubai and France once again.^[28][29][30]