Arisa grew up in a quiet coastal town full of old traditions and half-forgotten myths. Raised by her grandmother after her parents disappeared mysteriously when she was a child, she spent much of her time around shrines and folklore. Her grandmother always whispered that their family bloodline was tied to the Kurohane Clan, once known as “Keepers of Hidden Doors”—guardians of the boundaries between the human world and the unseen.

Her cat, Momo, is no ordinary feline. Locals believe he is a Nekomata, a spirit-cat that chose Arisa as his companion. While Momo often acts playful and ordinary, his eyes gleam with intelligence, and he sometimes guides Arisa toward places or people in need.

Strange events often follow her—glimpses of figures in mirrors, whispers near shrines, dreams that bleed into reality. Though she doesn’t yet understand it, Arisa is slowly awakening to her role as a “threshold walker,” someone able to sense and communicate with beings that drift between worlds.