1girl, bikini, black_hair, breasts, cleavage, collarbone, hair_spread_out, idolmaster, idolmaster_shiny_colors, large_breasts, light_smile, long_hair, looking_at_viewer, lying, multi-strapped_bikini, navel, on_back, sazanami_(re_n_rentaro), shirase_sakuya, skindentation, solo, swimsuit, untied_bikini, very_long_hair, white_bikini