In a world where humans sell and buy otherworldly species as slaves, the great mage Rifenhardt is treated like the Demon King for helping the otherworldly species. A party of heroes arrive to bring down the Demon King! Rifenhardt succeeds in greatly injuring the heroes, but he faces death at the hands of... the Martial King Tesslon! "Time and Space Regression Spell." However, Rifenhardt miraculously manages to cast this last-resort spell and regresses to the past. But... “Who are you?” He awakens reincarnated in the body of the continent’s strongest physical warrior, Tesslon! Now begins Rifenhardt's adventures as both a great mage and the physically strongest man to change the world!