Anime illustration of a beautiful big sister with long straight black hair and a serene expression, her upper body that of a pale-skinned woman in her mid-20s wearing a loose, flowing white yukata with wide sleeves and subtle floral embroidery partially open at the chest, her lower body transforming seamlessly into massive octopus tentacles with glistening suckers, muscular undulations, and iridescent pinkish-blue hues, captured in a medium shot from a slight low angle underwater. She floats gracefully with arms extended outward, hands gently trailing water currents, tentacles curling dynamically around her in a protective coil, gazing softly upward with half-lidded eyes and subtle smile. Sunlight shafts pierce the crystal-clear turquoise ocean depths, illuminating bioluminescent particles, coral fragments, swaying kelp strands, and distant schools of tiny fish, bubbles rising from tentacles. High detail on wet fabric textures clinging to skin, slick tentacle membranes, hair strands floating ethereally, great quality with sharp lines, vibrant yet cool blue-green palette, dreamy mystical atmosphere.
