2girls 98-tan 98se-tan arms_behind_back ass bad_id bad_pixiv_id beach bikini blue_eyes blue_hair bob_cut cloud day dd_(ijigendd) hair_bobbles hair_ornament hairpin horizon innertube looking_at_viewer looking_back multiple_girls navel ocean one-piece_swimsuit one_side_up os-tan outdoors ponytail purple_eyes purple_hair school_swimsuit short_hair sky striped swim_ring swimsuit water