Man, any time somebody licks an armpit, all I can think is "I bet antiperspirant tastes awful and is murder to get off your tongue." An ignorance I'm happy to take to my grave.
Deodorant is pretty rare in Japan (hard to even find in general stores) because they, along with most East Asians, have genes that makes their sweat have little to no odour. Hence why this fetish is mostly limited to hentai and asian porn.