Willem Kmetsch wakes up from his icy slumber as the last surviving Emnetwiht, a race of humans that populated the planet’s surface until they met their untimely demise five centuries ago at the hands of "Beasts." Currently, he lives among the hundred odd floating islands that make up civilization—otherwise inhabited by various other species, all of whom possess distinct animal-like features such as horns, fangs, wings, and scales. Because he lacks any such feature, Willem is referred to as a "markless."

One day, Willem encounters another markless named Ctholly Nota Seniorious. He thinks nothing of the meeting, and continues to spend his days working odd jobs until he runs into her again, this time after accepting a military posting. Willem soon learns that the group of bubbly young Leprechauns he is tasked to look after are pivotal in the ongoing battle against the Beasts. These girls, who have had little exposure outside a world where they are treated as weapons, are willing to die if it means defeating the Beasts.

Determined to nurture a life of normalcy for them, Willem soon becomes a father figure to the girls. Just like how he once went off to battle, he must now come to terms with watching these children go off to war.

Shuumatsu Nani Shitemasu ka? Isogashii desu ka? Sukutte Moratte Ii desu ka? ranked fifth in the 2016 Kono Light Novel ga Sugoi! in the Light Novels category. The series was published in English as WorldEnd: What Do You Do at the End of the World? Are You Busy? Will You Save Us? by Yen Press under the Yen On imprint from July 31, 2018, to December 10, 2019.