Anime-style illustration of Koakuma (Koakuma, “Koa”), a cute devil girl with long red hair and soft red eyes. She has a gentle, shy, and polite expression with a warm, quiet smile, giving a calm, kind, and studious impression. She has small delicate devil horns and subtle bat-like wings on both her head and her back, designed in a soft and non-threatening, decorative way. She wears a white shirt with a black to dark brown vest and a matching long skirt in the same color, styled neatly like a librarian uniform. A tidy necktie is worn properly at the collar, enhancing her orderly and intelligent appearance. The skirt has a thin white line near the hem as a simple accent. She is carefully organizing books, gently floating them into place on tall shelves inside a vast magical library. The environment is a quiet, endless library filled with bookshelves, warm soft candlelight, and faint floating dust-like magical particles. The atmosphere is calm, cozy, and slightly magical, emphasizing her role as a diligent, cute, and reliable library assistant.