Maou-sama no Mou Approach ga Overkill Sugimasu

24-hour surveillance of ex-lover's activities. A handsome demon king and an unlucky hero from a previous life. Despite his bad luck, Yuuki Yuta lives an ordinary life. One day, a handsome transfer student, Mazaki Rei, arrives at Yuta's school. Although it should be their first meeting, Rei's sense of distance from the very first day is a bit strange. When Yuta asks him why, he learns that Rei is the Demon King and that Yuta was a former hero in his previous life, And they were even lovers...! Until Yuta's curse is lifted, he and the Demon King begin a 24-hour, indefinite life of surveillance!