Humanity has Declined

Several centuries have passed since humanity began its quiet, irreversible decline, driven by a catastrophic drop in birthrates. In the wake of mankind's fading dominance, a new species has risen to claim the Earth: the Fairies. Standing merely ten centimeters tall yet possessing remarkable intelligence, these enigmatic beings have become the planet's most prosperous inhabitants, thriving where humans once ruled. To navigate this strange new era, the protagonist takes on the role of a United Nations arbitrator, tasked with mediating relations between the dwindling human population and the ascendant fairies. She returns to her rural hometown to assist her aging grandfather, expecting her diplomatic duties to be little more than a peaceful formality. Believing her position will be an easy one, she sets out to visit a nearby fairy habitat simply to introduce herself and establish goodwill. However, her casual greeting quickly spirals into something entirely unexpected, shattering her assumptions about both her quiet new life and the true nature of the world's inheritors.