Xolodnik

Kyle Meyers, an unambitious gamer, is unexpectedly transported to a fantasy world after a freak lightning storm strikes during his gaming session. Disoriented but unfazed, he soon encounters Princess Aria, her curious brother Alistair, and multiple other members of the royal family... The weird thing that everybody seems to believe that if the committed person (engaged, married, or in a relationship) initiates any sexual or romantic activity with Kyle—asking him on a date, kissing him, touching him, or explicitly inviting him to fuck—it does not constitute cheating on their partner.

18yo teen bumps his head and gets superpowers, what else do you need?