Humanity has Declined

It's been several centuries since human beings declined due to the steep drop in birthrates. The most prosperous species on the Earth are "Fairies", 10 cm tall creatures with high intelligence. I became a UN arbitrator between the humans and the fairies and returned to my hometown to help my grandfather. I thought my job would not be a tough one and visited one of the fairies' habitats to say hello to them but...

It's been several centuries since human beings declined due to the steep drop in birthrates. The most prosperous species on the Earth are "Fairies", 10 cm tall creatures with high intelligence. I became a UN arbitrator between the humans and the fairies and returned to my hometown to help my grandfather. I thought my job would not be a tough one and visited one of the fairies' habitats to say hello to them but...

For years, declining birth rates have forced what's left of the human race to cede more and more territory to other beings who have appeared to take advantage of the emptying ecological niche. Now, only a handful of humans remain among the remnants of civilization and Earth is dominated by faeries —tiny, ten-inch tall creatures of surprising intelligence. But humanity's importance isn't over quite yet, as young Watashi learns as she makes the decision to return to her hometown and assume her grandfather's position as an arbitrator between the races. Unfortunately, the job isn't going to be anywhere near as simple as she expected, and it's going to take a wisdom far beyond her years to achieve her most important mission.