The incident happened in Monday's LaLiga clash when the Equatorial Guinea international walked towards his bench after being replaced on 59 minutes.
A fan in the stands at Nuevo Los Carmenes stadium was caught on camera directing monkey gestures at the player.
Akapo stopped to talk to the individual, with another supporter also asking him to cease.
The defender notified the fourth official of the incident, and LaLiga reported the case to the local authorities.
In a statement on Wednesday, Granada said the perpetrator, who was not a club season ticket holder, has been reported to the public prosecutor's office.
Granada reiterated their "zero tolerance against racism."
Cadiz condemned the episode, while Akapo declared there is still work to be done in the battle against racism.
"One more episode of racism in football," Akapo said in a Twitter post on Tuesday.
"Fortunately, more and more people are aware, but there is still a lot of work to be done, and this means condemning racist attitudes and removing them from football stadiums, sports and our society."