Ünal is expected to join a Belgian Pro League within the next few days where he hopes to gain regular first-team football.
The 18-year-old striker did join City on the pre-season Australia tour and made an appearance in the 5-4 win over Roma on penalties last Tuesday. The young striker has now played two games for the Citizens with both ending in victory.
The Turkish international will not be playing in England next season due to not having the necessary work visa requirements. Ünal would have to be granted special permission by the FA to play football in the Premier League next season.
Ünal holds the record of being the youngest player to ever score in top-tier football in 2013 when he scored against Galatasaray.
The Turkish international was recently listed in the Guardian as one of the 40 best young talents in world football.