The 18-year-old turned out for his first game in a Genk jersey and impressed his new side on his unofficial debut.
Ünal joined Belgium side Genk on a two-year loan last week but City have the option to cut his temporary stay short next summer.
The 18-year-old striker will not be playing in England next season due to not having the necessary work visa requirements, he would have to be granted special permission by the FA to play football in the Premier League for the 2015-16 campaign.
Ünal holds the record of being the youngest player to ever score in top-tier football in 2013 when he scored against Galatasaray and made his international debut aged 17.
Genk play in the Belgium Pro League and Ünal is expected to gain first-team experience next season.