Yuki's been reborn in another world as a demon lord—and his new life is going swimmingly! He continues strengthening his dungeon with his makeshift family of monster girls until, one day, a heroine arrives on their doorstep to take down the demon lord. Or, at least, that's what she says before breaking into tears because the traps are too scary! Curious and unable to resist lending a helping hand, Yuki heads out to welcome the hapless heroine.
The group then decides to take a trip to a human settlement with their new friend. They all have a blast as they go around shopping, eating, and sightseeing, but the fun comes to an abrupt halt when a ghost appears out of nowhere and starts attacking the townspeople one after another. Can the demon lord who just wants to live the good life pass judgment on this new enemy?!