Isekaigaeri no Moto Yuusha Desuga, Death Game ni Makikomare Mashita

During a school trip, Kaito Ise and his classmates suddenly find themselves in the middle of a deadly game in which they must fight each other until one person remains. However, the organizers soon discover that Kaito is an “isekai returner” who had spent a decade in a fantasy world where even the smallest monsters posed great threats. After saving the fantasy world, Kaito returns to Japan only to find that only a few seconds have passed since his departure. All he wants is to enjoy his school trip and live a peaceful life.
Despite being up against a former “strongest man,” the organizers are no match for Kaito, who easily defeats them with his overpowered skills. However, new problems arise once things return to normal, and Kaito realizes that a peaceful life might be too much to ask for.