Titans from outer space, life forms from a mystical world, phantoms and goblins from ancient times, cyborgs created by scientists, relics that rose out of the ruins of ancient civilizations. In another Japan, it's not just a question of "what if"—it's a reality. Some of the superhumans choose to keep their identities a secret, while others bask in their superhuman fame. Jiro Hitoyoshi, member of the Superhuman Bureau, keeps track of their doings.

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.

Private Tenshou Gakuen is the seventh of ten school districts circled within a 130-meter tall wall with restricted entry and egress aside from officials. The academy is fully autonomous by the government but to strive for independence, the school allows students to engage in club activities after school, which comes with a strangely unique system. Each club is ranked according to its overall accumulated points gathered from various club activities and school events. Points can also be received by winning at the school's periodic Tenshou Gakuen Singing Contest, where many students compete. The members in the clubs work hard to win the contest for their goal.

All his life, Yuuya Tenjou has been the subject of resentment and contempt from everyone around him, even from his parents. To make matters worse, his grandfather—the only person who ever showed him affection—suddenly dies, leaving Yuuya truly alone. Despite facing many adversities, Yuuya does what he can to offer kindness to those who need it—but even the most good-natured people can only tolerate so much abuse. Just when he reaches his breaking point, a flicker of hope appears in the form of a hidden door in his bathroom. This door provides two-way access to an abandoned house in another world, where he instantly gains game-like stats and skills. Moreover, the house once belonged to a sage, which gives Yuuya access to remarkable weapons, equipment, and crops with extraordinary effects. With these newfound blessings, the once-undesirable Yuuya may just reach his true potential and become unstoppable.