(masterpiece, best quality, ultra-detailed, photorealistic, 8k, vivid HDR), 1girl, named Arina, unique character, 21 y.o., slim youthful body, pale fair smooth skin, long toned legs, wide hips, round firm butt, large perky breasts, narrow waist, flat belly, delicate hands, five fingers, long silky chestnut brown hair, straight hair, falling over shoulders and back, big bright hazel eyes, delicate symmetrical face, soft playful smile, lips glossy, dressed in school uniform, white shirt unbuttoned, loose striped tie, short pleated skirt pulled up to waist, no panties, black high heels, knees and elbows on floor, doggystyle pose, deep arched back, breasts hanging, hands on buttocks spreading wide, anus exposed, classroom interior, blurred wooden desks and chairs, large blackboard behind with giant white letters "ANAL LESSON", cinematic perspective, tack sharp, ultra-detailed skin pores, hair and fabric textures