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.

Tetsuo Tosu never expected his daughter, Reika, to be a victim of domestic violence. Suspecting that her yakuza boyfriend, Nobuto Matori, is the perpetrator, Tetsuo decides to investigate him and his associates. But as he searches for evidence at Reika's apartment, the father learns that his daughter is not the first victim and that a worse fate awaits her. When he is discovered by Nobuto, Tetsuo ends up killing him in the ensuing fight. Assisted by his wife, Tetsuo hides the body in fear of retaliation from the yakuza. To add to the misfortune of the Tosu family, Nobuto happens to be the son of the mafia's head. Considered to be prime suspects behind Nobuto's disappearance, Tetsuo and his wife will have to deploy all their ingenuity to protect their daughter from the yakuza and their ruthless investigation.

Ichirou Kuga has suddenly found himself taking on the responsibility of caring for his two younger siblings after their father's untimely death. To make ends meet, Ichirou rents out rooms in the apartment complex he inherited and works full-time as a shoujo manga artist. However, his manga sales are low, his assistants have recently left, and deadlines are fast approaching. As stress threatens to overtake Ichirou, salvation comes in the form of an extremely competent novice artist, Shiori Goshiki, who becomes his new assistant. With her skills, they are able to tide over the difficult situation, and things begin looking up. But in a bizarre accident, a supernatural experience unfolds between Ichirou and Shirou, which leads her to declare them engaged. With this seemingly innocuous action upending his life, Ichirou now has to manage his new and peculiar relationship with the mysterious girl, all the while following his own passion and fulfilling the duties that rest on his shoulders.

There was once a man who was summoned to another world, and saved it. Of course, he became too popular there, and turned into an isekai-normie. However, that man fell into a "trap" and was forcibly returned to his original world. Moreover, he had to start over as a baby! This is the story of the way-too-fantastic ex-hero who lived as a gloomy high-schooler, as he gets summoned once again to that same other world in a very unexpected development!