A powerful necromancer known as the Corpse God dies during a legendary battle, only to be reborn as Polka Shinoyama, a young boy in modern-day Tokyo. In the process of trying to adapt to his new physical body, he gets targeted by various groups that deal with the supernatural. Among them is Misaki Sakimiya, a high school girl who can see spirits and is out for his blood from the very moment they meet. Attempting to make sense of this situation where unknown parties want him dead, Polka eventually meets Takumi Kuruya, a contractor skilled in surveillance and hacking, and Lisa Kuraki, a crime boss operating out of Shinjuku. Alongside these—and other unexpected—allies, Polka braves danger to reveal the truth of his reincarnation and the fate awaiting the world he now lives in.

In order to pursue her dream of bringing positive changes to Japan, Mitsumi Iwakura leaves her countryside town to attend a prestigious high school in the hustle and bustle of Tokyo. As she has already mapped a clear life plan, she has absolute confidence that there will be zero mishaps from then onwards. Despite her ambitious promise, the country girl ends up running late on the first day when she gets lost on her way to school. Fortunately, she meets a fellow first-year student, Sousuke Shima, who is in the same situation and offers to go with her. They eventually make it to school, but the misfortunes do not end there, as Mitsumi leaves an unfavorable first impression in front of her classmates. Nevertheless, the class soon takes notice of her friendship with Sousuke despite their opposing personalities. Only time will tell whether Mitsumi will be able to forge fruitful relationships with her classmates, and she will certainly not be alone.

When Rinko Hanasaki dies in modern-day Japan, she awakens in the body of Raeliana McMillan, the eldest daughter of a nouveaux riche baron. However, this is no ordinary world; it's the exact same one as a novel she once read. Beloved by her family, it would seem as though she is in a fairy tale. But Raeliana is far from the main character—she is a mere plot device, whose murder at the hands of her fiancé instigates the entire story. Raeliana has no intention to accept her fate quietly. She sets her eyes on someone in a position of great power—the vieux riche male protagonist Duke Noah Volstaire Wynknight—aiming to completely change the original story. Using her knowledge of future events, Raeliana offers information to Noah on the condition that he acts as her fake fiancé, but the Duke's two-faced nature throws a wrench in her plans!

Fifteen years ago, disaster struck human civilization, and now dangerous man-eating monsters roam the ravaged lands, posing an existential threat to the remaining survivors. Amid this turmoil, an isolated facility shelters children and nurtures them in peace. However, as a few among them find out about the world beyond the narrow periphery of their nursery's walls, their curiosity about it slowly grows. Meanwhile, in the outside world, young survivors Maru and Kiruko band together to search for a special place called Heaven, each for their own reasons. Carrying past burdens and tragic secrets, the two hope to find answers to the cruelty they have experienced in their lives and in the world, which still remains in tatters.