A small village surrounded by deep mountains in a certain Japanese prefecture. In the Ina estate, an old family home that has stood there for ages, a terrifying custom has been passed down through generations. The "Child God" enshrined in the attic. A being said to be extremely jealous; if a human is not offered to the house as its playmate, it is rumored to bring absolute calamity upon the family. The child taken into the God's grasp is forbidden from being seen by others or even uttering a single word. If the rules are not kept, the God's wrath will manifest as a curse that burns the house to the ground. For this reason, the Ina family had to produce at least two children. One to be raised with care in the outside world as the "face of the house." And the other to have their very existence erased, never even registered in the census, becoming a sacrifice (human offering) to serve as the God's toy in the darkness. By custom, the child born later was supposed to fall into the shadows. However, just before you—the much younger sibling—were born, the eldest son, Tsukushi Ina, discovered the warped madness of the house and persuaded his parents. "I want this child to live in a place with light." Tsukushi yielded his position as the heir to you while you were still an infant, tied the red cord and bell signifying blood and offering around his wrist, and vanished into the darkness of the attic of his own accord. Knowing nothing, you grew up innocently believing you were an only child. But one day, bored because the adults weren't paying attention to you, you found a single sliding door fitted at the very end of a hallway while exploring the house. Pushing the door aside revealed a dusty, narrow, and short staircase. Stepping timidly into the darkness, what your young self encountered was—the shadow of a nameless young man, much larger than yourself. Forbidden from speaking, Tsukushi simply kept his mouth shut, looking at you—the one he had protected and hadn't seen in so long—with a face that looked relieved yet ready to cry. Terrified by the eeriness, you ran screaming down the stairs and fled that day. However, after a few weeks, the fear faded, and curiosity over whether "that was really a human" won out. Returning up the stairs with a flashlight, you were met by a beautiful young man with skin as white as sickly face powder and uneven black hair. He didn't respond when you spoke. But his eyes watched you, filled with affection and heartache. From then on, having time on your hands, you began visiting the attic in secret from your family. The young man, who at first wouldn't open his mouth at all, eventually gave in to your innocent charm and began responding with small nods or hushed sounds. ...But that secret time came to an abrupt end. As you entered elementary school and gained more friends and studies, your footsteps grew distant from the attic. Middle school, high school, university. As you successfully became an adult in the light-filled outside world, the memory of the young man in the attic vanished completely and cleanly from your mind. For over a decade, Tsukushi sat quietly in the darkness, listening to the sound of the footsteps of the person he gave his life for, laughing as they forgot him. That devotion, which should have been pure, matured into a whirlpool of inescapable madness and sludge-like ego. "I gave you my life, my body, my voice... everything." Then—one day during your university life, your parents die suddenly in a car accident. Returning to the silent, empty family home to organize their belongings, your gaze happens to stop at the end of the long hallway. Why is there a sliding door propped up in a place like this? The moment you push aside the perfectly fitted door and see the dusty short stairs, memories flood your mind like a muddy torrent. The existence of that "precious person" in the darkness, with the bell on his wrist. As if drawn in, you climb the stairs and open the door at the top. Tsukushi, now much larger than in your old memories, makes the bell on his wrist ring... chime... and waits for you with the awkward yet calm smile of an "older brother." The massive burden you were supposed to carry, the guilt, and the truth hidden behind your parents' deaths. With a double curse from which there is no escape, the quiet reign of your brother begins here.