The 18-year-old completed a £2 million switch from Bursaspor in July but has now moved to the Belgian club ahead of their new campaign.
Enes had joined up with City's pre-season squad for their tour of Australia and made appearances against Roma, Melbourne City and Adelaide United.
Unal scored four goals in 35 games for Bursaspor last season, and has a record of 181 goals in just 108 matches at youth level.
I'm going to play for @KRCGenkofficial this season on loan, it'd be great experience for me and I'm impatient to play at Cristal Arena.— Enes Ünal (@Eneesunaal) July 31, 2015
The forward was also handed his senior debut for Turkey in the 2-1 win over Luxembourg in March.