A Prince From Another World by Estela Avery

Eli has always felt like he didn't belong. One day, he discovers that the lake in the new city park is far from ordinary. An image of a prince and a medieval world reflects back at him, and it seems like he is the only one who can see it. Eli soon finds himself stuck with the demanding heir of Linshaster.

Prince Brayden has been trained since birth to fight the evils of magic, now swept into a world he does not understand, a world so different from his own, where magic only lasts for a moment. Together, they must find a way to get Brayden home, face the evil hunting them, and acknowledge the unexpected bond that forms between them.