After Jinta and Suzune ran away from their home as children, they were taken in by Motoharu—the virtuous sentinel of Kadono Village—and his daughter, Shirayuki. The settlement was ruled by its shrine maiden, Itsukihime, whom only a select few were allowed to interact with. When Itsukihime passed away, Shirayuki was appointed in her place. Wishing to stay in contact with her, Jinta worked diligently for years and was finally selected as the next sentinel. As the protector of the village, Jinta's duty is to eliminate any threats. One day, he encounters a demon in a nearby forest. At the end of the battle, the demon makes a proclamation about the destined ruler of all demonkind. He attaches his severed arm to Jinta, turning him into an unaging demon man. By the time Jinta comes to, Kadono is on fire. Suzune has transformed into the demon from the divination, and due to a series of misunderstandings, she murders Shirayuki and flees. Devastated, Jinta cannot forgive Suzune for her actions; he departs on a journey to find her. As Jinta travels around Japan across the eras, he endeavors to protect as many people as possible from aggressive demons. In his quiet moments, he contemplates what he should do when he once again faces his childhood friend.

Humanity and demonkind have been on bad terms for millennia, resulting in the continent of Leunders being split in two. Although the situation has stabilized between the races, the fragile peace breaks when the new demon king launches a fierce all-out attack. With all of the non-demon nations falling to the violence in under a year, humanity's hope rests in a special squad, led by swordsman Kyle Leonard, that must assassinate the demon king in order to bring an end to the war. During the dangerous mission, Kyle ends up in a clash with the demon king that brings him to the brink of death. As Kyle realizes he has lost everything he wanted to protect, a mysterious gem transports him back in time before the conflict even started! Now with knowledge of future events and a strong desire to save his loved ones, Kyle sets out to become even stronger to prevent the extinction of humanity.

Hinata did it. He got reincarnated into another world, took up the mantle of Hero, and slew the dreaded Demon Lord alongside his party of fellow adventurers. As his reward, he's returned to Earth to resume a normal life. Or it would be if it wasn't for the fact that his dark elf companion Mariabelle decided to travel to Earth to come and live with him! Now she uses her arcane talents to ward off any potential romantic rivals and capture Hinata's affection.

After a disastrous romantic confession, Masamune Okumura finds solace in the fictional world of anime and manga. Now a second-year high school student and the president of the Manga Research Club, Masamune spends a peaceful existence watching the adventures of the angel Liliel, his favorite character. In the beginning of the academic year, Masamune’s life is turned upside down when he meets first-year student Ririsa Amano, a passionate cosplay practitioner. Despite Masamune's initial reluctance, the determined young woman manages to convince him to become her personal photographer for the production of a collection dedicated to their common favorite character: Liliel. As Masamune enthusiastically discovers the world of cosplay and photo editing, he is unexpectedly reunited with his childhood friend Mikari Tachibana, who has become a model in the hope of impressing her beloved upperclassman. Realizing that modeling is not enough to intrigue the hopeless otaku, Mikari decides to join the club and become a cosplayer herself, all to finally have a chance at winning Masamune's heart. However, Masamune's love for fictional characters may not be capable of extending to those who impersonate them.