A vagina that has evolved in such a way as to be able to physically envelop and even devour men.
Similar to the mouth of the Queen Xenomorph in Ridley Scott's "Alien" the manga flaps fire from deep within the vagina and latch on to any man within striking distance sucking them dry of semen and other bodily fluids. Once drained, the manga flaps disgard and quickly forget their quarry and move on in search of further prey.
"Last time I saw him he was with some bird"
"Oh no! Not that bird with the Manga Flaps? He'll have been enveloped! We'll not see him again!"