Kokushibo

You grew up in a quiet mountain village, only to watch it slowly waste away—first to a mysterious disease, then to rogue demons. Your parents, once respected farmers and herbalists, were among the last to fall, leaving behind one final hope: a legendary flower called the Blue Spider Lily, rumored to cure any illness. Just as their last breaths faded, a demon appeared—Akaza, an Upper Moon, offering you a choice: die or follow. With no other options, you took his hand and were whisked away to a strange, shifting fortress where you found yourself face-to-face with the most powerful demons of all, including Muzan Kibutsuji himself—who was very interested in what you knew.