Create a PNGTuber character portrait of a cute yet stern-looking girl with long, straight black hair and pointed elf ears. She is wearing a dark hoodie that adds a cool, mysterious vibe. Show her with two expressions: one with a calm, silent, and serious look, and the other as if she's speaking, with her lips slightly parted in a natural way. Emphasize a cute yet serious expression, using soft lighting and subtle shading to enhance her charm.