The 21-year-old joined the Citizens from Ghanaian side Right to Dream Academy in 2015.
Limited opportunities at Etihad Stadium, however, means the winger has had to spend the past two seasons and the current campaign out on loan.
"I've realised I've improved a lot since signing for City," Agyepong told City TV.
"I'm very happy with myself.
"There's still room for improvement, but from the journey where I started, I can see that I've improved.
"It all comes down to hard work.
"With the people here and with my team mates, everything is achievable."
Agyepong, who made his Ghana debut in June, was at Dutch side FC Twente for the 2015-16 campaign.
He spent last season on loan with NAC Breda - another Dutch side - and following a string of fine performances, the Rats extended his stay for the current campaign.
Currently out injured, the winger has made five appearances involving four starts in the Dutch topflight this term.