Daemons of the Shadow Realm

Yuru lives in a sealed mountain village called Higashi, hunting birds and caring for Asa, the twin sister kept inside a cage for a ritual duty. The village treats its customs as the whole world, but that order breaks when armed outsiders arrive with creatures called Daemons and modern weapons Yuru has never seen. The Asa beside him is revealed to be a substitute, and the real Asa has been living outside in the modern world. During the attack, Yuru releases the guardian pair known as Left and Right and becomes a Daemon user himself. Dera helps him escape, but the flight only opens more questions about why his parents disappeared, why the village was isolated, and why twins born at the border of day and night are feared by every faction looking for Daemon power.

Outside Higashi, Yuru enters a world of cities, firearms, hidden clans, and users who fight through paired Daemons with specialized abilities. Asa is not waiting as a helpless captive. She has her own protectors, her own knowledge, and a brutal way of surviving after years away from her brother. The Kagemori family, village survivors, and other groups all move around the twins because their birthright may let them command all Daemons. Yuru has to learn how to fight with Left and Right while deciding whom to trust when almost every explanation is incomplete. Asa searches for him from the other side of the conflict, but reunion does not mean safety. Their shared origin points to a larger disaster, and the more they learn about the Shadow Realm, the clearer it becomes that their separation was part of a struggle that began long before either twin understood their own name.