He is a two-time European junior champion (2012 and 2013) and a gold medalist in the boys' 10 m air pistol at the 2014 Youth Olympic Games in Nanjing, China.

[1] Coming from a sporting pedigree, Korostylov also shares the same discipline with his older sister Yuliya Korostylova, who competed in pistol shooting for Ukraine at the 2004 Summer Olympics in Athens.

[3][4] Korostylov flourished his early sporting success at the 2014 Summer Youth Olympics in Nanjing, China, where he fired a final junior world record at 203.4 to secure a gold medal victory in the boys' 10 m air pistol, surpassing then 14-year-old South Korean shooter Kim Cheong-yong by a solid 3.6-point lead.

[2][5] On his senior debut at the inaugural 2015 European Games in Baku, Azerbaijan, Korostylov finished fifth in the men's 10 m air pistol final with an astonishing score of 138.2, beating his teammate Oleh Omelchuk by more than twenty-two points.

With four other shooters ahead of him having already filled their Olympic quotas in the previous qualification tournaments, Korostylov was guaranteed a place on the Ukrainian squad, and competed for Ukraine at the 2016 Summer Olympics in Rio de Janeiro, finishing in qualifying in 35th place, missing the final round.