In the autumn he was unbeaten in three starts, winning the Kobe Shimbun Hai, Kikuka Sho and Arima Kinen and took the JRA Award for Best Three-Year-Old Colt.

He is from the sixth crop of foals sired by Deep Impact, who was the Japanese Horse of the Year in 2005 and 2006, winning races including the Tokyo Yushun, Tenno Sho, Arima Kinen and Japan Cup.

[5] In the Satsuki Sho over 2000 metres at Nakayama Racecourse on 17 April Satono Diamond was made the 1.7/1 favourite ahead of the Japanese champion two-year-old colt Leontes in an eighteen-runner field.

[6] After racing in mid-division the favourite made a forward move in the straight but was slightly hampered in the closing stages and finished third behind Dee Majesty and Makahiki.

[8] After a break of almost four months, Satono Diamond returned to the track in the Kobe Shimbun Hai (a major trial race for the Kikuka Sho) over 2400 metres at Hanshin on 25 September.

"[10] In the 77th running of the Kikuka Sho over 3000 metres at Kyoto on 23 October Satono Diamond started the 1.3/1 favourite in an eighteen-runner field which included Dee Majesty, Mikki Rocket and Air Spinel.

[12] On 25 December Satono Diamond was matched against older opposition when he was one of sixteen horses invited to contest the Arima Kinen over 2500 metres at Nakayama.

[15] On 30 April the colt faced a rematch with Kitasan Black in the spring edition of the Tenno Sho over 3200 metres at Kyoto and started 1.5/1 second favourite behind his older rival.

[16] On his first run as a five-year-old Satono Diamond finished third to Suave Richard in the Kinko Sho over 2000 metres at Chukyo Racecourse on 11 March.

Three weeks later he started third choice in the betting for the Grade 1 Osaka Hai at Hanshin but was "never a threat" and came home seventh behind Suave Richard, beaten six and a quarter lengths by the winner.

He disputed the lead with the eventual winner Mikki Rocket early in the straight but then faded in the closing stages to finish sixth.

[18] The horse returned to the highest class for his next race and ran sixth behind Almond Eye in the Japan Cup at Tokyo on 24 November.

Satono Diamond ended his season on 23 December with an attempt to repeat his 2016 success in the Arima Kinen and came home sixth of the sixteen runners behind Blast Onepiece.