After five brutal years fulfilling his duty as an isekai hero, Isami Oibi finally returns home to Earth. Expecting a peaceful reunion with his normal life, he discovers that 30 years have passed in Japan while he was gone, and Earth itself has transformed into a modern society where magic is common place! Emotionally drained, battle-weary, and seeking nothing more than quiet obscurity, Isami hides his identity as a returned hero. However, his unmatched aura continuously draws interested parties to his side. To make matters worse, dark cultists seeking to resurrect demons are lurking in the modern magical world, forcing this thoroughly burnt-out former hero to accidentally unleash his ultimate power once again!