Fourteen-year-old Suzuki Iruma has just been abandoned and sold to a demon by his irresponsible parents! Surprisingly, the next thing he knows he's living with the demon who has adopted him as his new grandson, and has been transferred into a school in the demon world where his new "demon" grandfather works as the principal. Thus begins the cowardly Iruma-kun's extraordinary school life among the otherworldly as he faces his true self, takes on challenges, and rises to become someone great.

In 2062, two decades after the failure of a massive workforce automation project. However, Artemis, the artificial intelligence at the core of that project, had decided to attack humanity, and the resulting war laid waste to Earth.

Considered a genius due to having the highest grades in the country, Miyuki Shirogane leads the prestigious Shuchiin Academy's student council as its president, working alongside the beautiful and wealthy vice president Kaguya Shinomiya. The two are often regarded as the perfect couple by students despite them not being in any sort of romantic relationship. However, the truth is that after spending so much time together, the two have developed feelings for one another; unfortunately, neither is willing to confess, as doing so would be a sign of weakness. With their pride as elite students on the line, Miyuki and Kaguya embark on a quest to do whatever is necessary to get a confession out of the other. Through their daily antics, the battle of love begins!

Inside a vast, self-replicating city bent on eliminating all life, mysterious loner Killy emerges to guide a remnant of humanity desperate to survive.