Chikyuu no Houkago

A mysterious threat known as "Phantoms" has killed most of the human population. Four individuals—Masashi, a reliable teenage boy; Sanae, a shy girl; Yaeko, a more outgoing girl; and Anna, a young child—have come together as potential last survivors of humanity. They live in a quiet, isolated way, maintaining a sense of normalcy amid the ruins. They describe their situation as an endless "after school" waiting period, as if expecting others to return. Over time, they notice unusual occurrences and realize the Phantoms are still present. Their days together are marked by uncertainty as they attempt to understand the fate of the world.