Humanity has Declined

Several centuries have passed since humanity entered a state of irreversible decline, driven by a catastrophic and sustained drop in birthrates. As human civilization slowly faded into obscurity, a new dominant species emerged to claim the Earth. These successors are the "Fairies"—diminutive beings standing merely ten centimeters tall, yet possessing an astonishingly high level of intelligence that has allowed them to become the planet's most prosperous inhabitants. In this transformed world, the protagonist serves as an official arbitrator for the United Nations, tasked with mediating relations between the dwindling human population and the flourishing fairies. Seeking a quieter life, she returns to her rural hometown to assist her aging grandfather. Confident that her diplomatic role will be a simple and undemanding affair, she sets out to visit a nearby fairy habitat, intending only to introduce herself and establish friendly contact. However, her expectations of an easy assignment are quickly upended when her initial encounter with these enigmatic creatures takes an entirely unforeseen turn.