![1girl absurdres armpit_crease armpit_cutout azur_lane bangs black_leotard blue_legwear blue_sky blurry_foreground blush bow braid breasts casablanca_(azur_lane) casablanca_(cheer_squad_on_break)_(azur_lane) cellphone cellphone_picture cheerleader cleavage cloud commentary_request core1013 covered_navel cowboy_shot crop_top day drop_shadow eyebrows_visible_through_hair hair_between_eyes hair_bow heavy_breathing high_ponytail highres large_breasts leotard leotard_under_clothes lifted_by_self long_hair long_sleeves looking_to_the_side midriff miniskirt open_mouth phone pleated_skirt purple_bow purple_eyes ribbed_legwear sidelocks silver_hair skirt skirt_lift sky smartphone solo_focus standing steam sweat taking_picture taut_clothes thighhighs two-tone_skirt wall white_skirt rating:s score:34 post #3858418](/cdn_image/preview/21/6a/216a6c173779a601e404bb805a010c2e.jpg)
Refers to the fold of delicate skin visible between the character's torso and arm that can still be seen when the inner portion of the armpit isn't visible, e.g. because the arm is lowered or the armpit is turned away from the viewer's perspective. See post #2958458, post #3398674, and post #3695398 for examples of what should be tagged as an armpit crease.
This tag was borne of efforts to disambiguate armpit peek (forum #140761) and was never intended to be used for completely visible armpits. For images where the entire armpit can be seen, just use the armpits tag.
Erroneously called an 'armpit vagina'.