Koku Akanbi: The Heart of Midnight by Maria Motunrayo

When 13-year-old Koku Akanbi accidentally unleashes a demon on a school trip, he has no idea what he's set in motion. Suddenly Koku is whisked away from his life in London and transported to his family's homeland of Olori, a mysterious place in which darkness is about to disappear forever - along with the magical creatures living within it. Accompanied by two super-powered sidekicks, Koku embarks on a mission to save Olori - and unlock his own extraordinary power...