2007

In 2007, Deep Sky was two years old, and was left in the care of the trainer Mitsugu Kon. Deep Sky made his debut in October 2007; however he was unable to win in the four races he raced as a two year old.^[1]

2008

Deep Sky raced six times and finally won for the first time at the end of January 2008. Deep Sky also bested the horse Katsutoshi two races afterwards, but neither was able to win. However, Deep Sky won in Mainichi Hai at the end of March 2008, allowing entry in the NHK Mile Cup which is one of the big races for a three-year-old horse.

Deep Sky entered the NHK Mile Cup on schedule. Deep Sky ran through the inside, and by the last straight overtook Black Shell. Deep Sky was then entered in Tokyo Yūshun and subsequently won the race.^[2]

After winning the Tokyo Tokyo Yūshun, Deep Sky took a prolonged break with either the Kikka Sho or Tenno Sho in mind as his next race.^[3] He won the Kobe Shimbun Hai in September 28, which was a trail race for the Kikka Sho, but ultimately opted to run in the Tenno Sho.^[4] At the Tenno Sho, Deep Sky finished third behind the more favored Vodka and Daiwa Scarlet.^[5] The following month Deep Sky ran in the Japan Cup, where he raced with Vodka once again. Deep Sky was able to best Vodka this time, but both lost to Screen Hero.^[6]

2009

At the awards ceremony for the JRA Awards, Kon announced that he intended to race Deep Sky at the Prix de l'Arc de Triomphe if the horse won that year's Yasuda Kinen and Takarazuka Kinen.^[7] However, Deep Sky was not able to win either races, with the horse losing once again to Vodka at Yasuda,^[8] and to Dream Journey at Takarazuka.^[9] The horse was put to pasture at the Fantast Club in Hidaka with the intention to race in the autumn season again. It was there, however, that the horse's left forearm was found to be suffering from tendonitis, and the decision was made to retire him to stud soon after.^[10][11] A retirement ceremony was held at Sapporo Racecourse on August 30 and his JRA registration was taken down.^[12]