After working himself to death in a hostile corporate environment, Yuuji Sano gets a second chance when he transmigrates to a game-like fantasy world. Although he wishes to lead an unassuming life, Yuuji learns that he has the title of a Monster Tamer, the weakest rank of adventurer. With his newfound skills, he tames a number of slimes around him and, with their help, acquires magical powers to become a Sage—a second profession that capitalizes on such potential. Even after gaining overwhelming strength, the scars from the life Yuuji left behind keep him from going all out. However, he might not be able to hide his abilities for much longer, as unforeseen dangers threaten to destroy the world that is now his only home.

A normal high school boy Kisaragi Ryuji's peaceful life is turned into an adventure by the return of his second cousin Eriko. Ryuji and Eriko seize a relic box from a black broker. In the box, they find a red dragon girl Rose. In order to protect Rose from the black organization, Ryuji decides to fight using his power as a relic handler.

Dog Days takes place in the world of Flonyard, an alternate Earth inhabited by beings who resemble humans, but also have the ears and tails of specific animals. The Republic of Biscotti, a union of dog-like citizens, has come under attack by the feline forces of the Galette Leo Knights. In an effort to save Biscotti, Princess Millhiore summons a champion from another world in order to defend her people. That champion is Cinque Izumi, a normal junior high student from Earth. Agreeing to assist Biscotti, Cinque retrieves a sacred weapon called the Palladion and prepares for war. In Flonyard, wars are fought with no casualties and are more akin to sports competitions with the goal of raising money for the participating kingdoms. Cinque is successful in his role as Biscotti’s champion, but learns that a summoned champion cannot be returned to their home world. The scientists of Biscotti will endeavor to find a way for Cinque to return home, but until they figure something out, he must serve Princess Millhiore by continuing to fight as Biscotti’s hero.

The great Jahy will not be defeated! Simultaneously combating starvation, the lack of A/C, and the unavoidable weakness of turning child-sized, Jahy—previously the second strongest being in the Dark Realm—is under great stress. If it weren't for the destruction of the mana crystal which used to power the Dark Realm, Jahy would still be living a life of power and luxury. And yet, at the moment, brawling with the landlady over rent is a recurring event for Jahy. Just to have a place to stay and food to eat, Jahy must work part-time. However, her immense pride will not allow her to live under such poor conditions for any longer than necessary. Vowing to reinstate the Dark Realm to its former glory, Jahy continues her journey to reassemble the mana crystal.