He is from the fourth 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] Mikki Isle began his second campaign in the Grade 3 Nikkan Sports Sho Shinzan Kinen at Kyoto on 12 January in which he started the 0.6/1 favourite and won by half a length from Win Full Bloom.

[6] On 1 March the colt started odds-on favourite for the Grade 3 Arlington Cup at Hanshin and recorded his fourth consecutive victory as he came home three and a half lengths clear of Tagano Grandpa.

[10] Three weeks later the colt started favourite for the Mile Championship at the same track but after taking the lead in the straight he faded rapidly and was eased down by Hamanaka and finished unplaced behind Danon Shark.

[11] On his 2015 debut Mikki Isle was beaten a nose by the six-year-old Daiwa Maggiore, to whom he was conceding five pounds in weight, in the Grade 3 Hankyu Hai over 1400 metres on heavy ground at Hanshin on 1 March.

At the end of the month the colt was dropped back in trip for the Grade 1 Takamatsunomiya Kinen over 1200 metres at Chukyo Racecourse in which he produced a strong late run down the centre of the track but was beaten half a length and a nose behind the Hong Kong challenger Aerovelocity and Hakusan Moon.

After tracking the leaders he went to the front 100 metres from the line but was overwhelmed by fast finishers in the final strides and was beaten into fourth place behind Straight Girl, Sakura Gospel and Ukiyono Kaze.

For his final run of the year the colt was sent to Sha Tin Racecourse for the Hong Kong Sprint in which he finished seventh to the locally trained Peniaphobia after fading in the straight.

The horse made his seasonal debut in the Hankyu Hai on 28 February and recorded his first victory for fifteen months as he won by three quarters of a length from the gelding Omega Vendetta.

Mikki Isle led from the start, fought off a sustained challenge from Neorealism and prevailed by a head from Isla Bonita despite hanging left in the closing stages.

[16] On his final racecourse appearance, Mikki Isle started favourite for the Hanshin Cup on 24 December but came home sixth of the fifteen runners behind the three-year-old Shuji.