Dimension Guard In Elite Class

Achill Rey is a Dimensional Guardian. A Dimensional Guardian is someone who has the task of guarding every world in his dimensional realm from various imbalances and creatures of chaos. At this moment, Rey suddenly analyzed that the next world that the chaos creatures would target would be the Classroom Of The Elite world within 2 to 3 years from now. This causes Rey to immediately come to that world in anticipation of the arrival of the chaos creature. While waiting for the creature to arrive, Rey is suddenly interested in school activities. This causes Rey to suddenly enroll in one of the best schools in the world, the Tokyo Metropolitan School. So how's the continuation of Rey's story of attending the Tokyo City Metropolitan School while waiting for the arrival of chaos creatures? Please follow the story.