![1girl aqua_(konosuba) aqua_eyes aqua_hair armpit_crease ass bare_shoulders blue_shirt blue_skirt blurry bow bowtie breasts commentary_request depth_of_field detached_sleeves hair_ornament hair_rings hand_up highres kono_subarashii_sekai_ni_shukufuku_wo! long_hair long_sleeves looking_at_viewer medium_breasts miniskirt noeru_(gt17854) parted_lips pleated_skirt shirt signature sitting skirt smile solo thighs rating:s score:28 post #3834817](/cdn_image/preview/e2/ca/e2ca22d8bda5d1c4e263beb31c7f4f9f.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'.