When aliens known as the Oni threaten to invade the Earth, they promise to leave under one condition—a randomly-chosen human must win a one-on-one game of tag against Lum, the beautiful daughter of the Oni leader. The "lucky" person selected happens to be the lustful and unlucky high schooler Ataru Moroboshi. Given 10 days to attempt to grab Lum's horns, Ataru realizes how impossible the challenge is as he is faced with Lum's extraterrestrial powers. Motivated by a promise of marriage from his childhood friend Shinobu Miyake, Ataru manages to catch Lum off guard. He mistakenly grabs hold of her bikini top first, but he eventually achieves his true goal. Although the game is over, Lum misunderstands that she is the one whom Ataru wants to marry, and she decides to move in with him. The poor student constantly tries to shake off the clingy Lum while doing his best to reconcile with his desired fiancée. After Ataru's heroic feat results in such a disastrous outcome, it is questionable whether luck will ever be on his side.

In Raja, a small country located to the west of Tempest. Rimuru and his companions get involved in a long-running conspiracy that swirls around the mysterious power of the queen. Rimuru and his commander Benimaru also encounter another ogre survivor named Hiiro, a man that used to be the brother of Benimaru.

Self-professed "home security guard" Mahiro Oyama has not left his home in years, secluding himself in his room playing erotic visual novels. This depraved lifestyle causes his prodigious sister, Mihari, to worry about his well-being. In hopes of solving this problem, she devises a plan to rehabilitate him back to normalcy. The first part of Mihari's plan is to concoct a medicine that changes her brother's biological constitution into a bona fide female, much to Mahiro's vehement dismay. Stuck in this predicament, Mahiro has no choice but to live out his life as a cute girl until the effect wears off—if it ever does.

On a rainy afternoon, a male high school student awakens freezing on the streets with no memory of how he got there. His classmate and crush, Karen Inukai, finds him and takes him back to her home where, to his surprise, she starts to undress. She seems intent on bathing with him, though he has no idea why. When she holds him once more, he catches a glimpse of himself in the mirror—discovering that he has turned into a dog! Inukai adopts the puppy and names him Pochita. Now, he must adjust to life as a dog and figure out how to get out of this strange predicament. But while he mulls over an escape plan, Pochita sees a whole new side to Inukai that he never saw at school.