happy birthday (artist), original, highres, 1girl, :o, ahoge, ass, back, bikini, blonde hair, blue eyes, blush, cloud, day, embarrassed, female focus, flat chest, from behind, hair bun, innertube, leaf, light rays, looking back, open mouth, outdoors, polka dot, polka dot bikini, polka dot swimsuit, short hair, single hair bun, sky, solo, standing, sunbeam, sunlight, surprised, swim ring, swimsuit, tankini, torn clothes, wading, water, wet