1girl, animal ears, balloon, bed sheet, fake animal ears, flat chest, fukumaru koito, heart-shaped innertube, idolmaster, idolmaster shiny colors, looking at viewer, lying, neckerchief, nonbire, on back, one-piece swimsuit, pillow, rabbit ears, sailor collar, smile, solo, swimsuit, thigh strap, twintails, wavy hair, white neckerchief