While saving a child from harm, otaku Asahi Ikusaba is transported to another world and believes he has reincarnated with cheat skills similar to those of the characters from his favorite games and novels. Unfortunately, reality strikes when an encounter with a powerful monster shows that he is still nothing more than an average person. In this moment of extreme danger, Asahi instinctively calls out to his overly doting sister, Maya, who appears out of nowhere, possessing the overpowered abilities he thought he had. Maya is ecstatic to see her brother again and resolves to use her newfound powers to protect Asahi no matter what. Together, the close-knit siblings attempt to find a way back home while enjoying their new lives. However, it soon becomes clear that their arrival in this world may have had a purpose. With the Demon King's overwhelmingly powerful army approaching, no one but Maya seems to be able to stand in its way.

On his way to a convenience store, Kazuya Shiina tries to defend two young girls from an armed assailant, only to end up getting stabbed himself and dying on the spot. This good deed allows him to be reborn with all his memories in another world as Cain von Silford, the third son of a margrave. When Cain turns five, a baptismal ceremony in the church grants him an audience to the seven gods who preside over the world. Not only do the gods fill him in on the circumstances of his reincarnation, but they also give Cain their respective divine protections—allowing him to use cheat-like abilities in swordsmanship, magic, and many other aspects. With these blessings, Cain sets out to live a fulfilling life that he deems a dream come true. However, it soon becomes clear that the gods have more plans for him than just a haphazard bestowal of overwhelming power.

Far to the north of the world lies Hell's Gate, a portal formerly used by the Demon Lord to invade the human realm. Thanks to the legendary hero Shion Bladearts, wielder of Excalibur, and his loyal band of companions, the Gate was sealed off and the demonic threat was vanquished. Unfortunately, the seal was incomplete and has begun to weaken, allowing the demons to once again begin their attack. Worried about the safety of his village, selfish and perverted farmer Touka Scott dig pitfalls to defend against the demons. But fear not, for Shion is on his way to reseal Hell's Gate and save humanity! Or at least he was, because the legendary hero is dead, having fallen into one of the pitfalls Touka dug. Luckily, dealing with the dead is the specialty of necromancer Anri Haynesworth. While she can't revive him, Anri can at least salvage their quest by forcing Touka's soul into Shion's rotting body and dragging him along to Hell's Gate in Shion's place. Not wanting to be left behind, Touka's childhood friend Yuna Yunis tags along. Together, the three of them set out as what just might be the most unsuitable party to ever try to save the world!

After surviving a brutal terrorist attack on Plant Quetta, Suletta Mercury returns to dueling at the Asticassia School of Technology, while Miorine Rembran sits at her injured father's side, waiting to see if he will recover. As the residents of Earth House are preoccupied with their respective troubles, two members of Dawn of Fold—the perpetrators of the attack—secretly infiltrate the school, putting Suletta and her friends at risk. At the same time, Prospera, Suletta's mother, approaches Miorine to propose the continuation of "Quiet Zero"—a project headed by Miorine's father that can allegedly end all war. Prospera seems to be another political figure with hidden, opposing motives, and whether she truly has Suletta's well-being at heart remains to be seen.