Okuto Nakamura is a timid and gloomy-looking student who cherishes only two things in this world: his pet octopus and his kind-hearted classmate, Aiki Hirose. Ever since the school entrance ceremony, Nakamura has admired his jovial classmate, albeit from a distance due to his poor social skills. After mustering up all the courage within him, he finally decides to talk to Hirose. During this first attempt to make contact, an instinctive mistake turns the idea of friendship into a distant dream, as he creates a hilarious impression on his crush. At school, students are expected to cooperate on numerous activities together, meaning Nakamura gets to spend extra time with Hirose. Given these opportunities, can he successfully redeem himself and accomplish his goal of becoming good friends with Hirose?

Hundreds of years after the large-scale battle against the Nokkers in the city of Renril, the world is unrecognizable. Thanks to the immortal Fushi's efforts in dormancy, he has successfully created a world with modern infrastructure where he and every living species can live in peace. When he finally awakens from his slumber, Fushi is elated to try everything this new world has to offer and revive his friends from the past. While exploring, Fushi runs into Yuuki Aoki, a lively middle school student, who is quick to welcome him and his friends into the house. As the group settles into their new home and learns more about the modern world, Fushi meets Mizuha, Yuuki's friend, who resembles someone familiar to him. It turns out that Mizuha is the descendant of the Guardians: the people whose only goal is to keep Fushi safe. Like her ancestors, she grows fond of Fushi, which brightens up her life. However, as bizarre events occur when Mizuha approaches Fushi, it becomes clear that this new world is far from perfect.

Orphan Himari Momochi's only link to her late parents is the house they secretly bequeathed her, which she does not learn of until her 16th birthday. Thrilled by the opportunity to know more about her family, Himari arrives at the rumored haunted house and is bewildered to find three young men already living there: Aoi Nanamori, who identifies himself as the guardian of the place, and his two familiars, Yukari and Ise. Although they allow her to stay overnight, they warn her to leave the next day so she can avoid harm from ayakashi—wandering spirits that sometimes attack human beings. Surprisingly, Himari is unaffected by her spectral encounters and determined to move in to the residence. After she discovers that Aoi had become guardian unwittingly and is now confined to the property, forgotten by the outside world, her resolve only grows stronger. Touched by his story, Himari decides to find a way to free Aoi from his dim fate, and she convinces the three Momochi House protectors to accept her as their landlady. However, the mysterious Kasha who keeps sending hostile ayakashi to Himari's new home seems to have darker plans for Aoi's future.

Kazuma Satou, former NEET and current reincarnated adventurer, finally returns home after the incident at the Crimson Demon village. He is joined by his ever-reliable companions: self-absorbed goddess Aqua, one-trick pony arch-wizard Megumin, and masochistic crusader Lalatina Ford Darkness Dustiness. Following their recent exploits, the party is one step closer to vanquishing the Demon King and his armies—a terrifying task that Kazuma is eager to ignore for as long as possible. Things, however, are not going as smoothly as the group would like; they are constantly racking up debt, getting sidetracked during missions, and falling into traps due to their recklessness and eccentricities. As the party struggles with their perennial issues, they receive an invitation from a princess interested in hearing tales of the group's heroic deeds. Darkness' pleas to refuse the invitation only fire the others up to accept it, marking the start of yet another uncanny adventure with unforeseen consequences.