On many of the behind the scenes pictures he posts on twitter, you see someone holding up a paper cup with the male actor sticking their finger inside.
Anyone know what's up with that?
Huh... have never seen that. But interesting question so I will a stab in the dark.
Sticking finger in a cup, held up by a crew member? So the cup is not to be seen during a scene? In general I'd guess it's to prepare the finger for (1) enhanced sexual stimulation, including possible enhanced DISCOMFORT, as per discussion above or (2) enhance non-sexual comfort for whoever is gonna be probed by those fingers, or (3) enhance safety. So the function of the paper cup? (1) To make the fingers cold (freezing cold?) or hot (say 10-20 degrees hotter than body temp). (2) to warm (body temperature) or to lubricate the fingers? (3) disinfectant, vitamin-E? ginseng? or some homeopathy?
On further analysis: (3) seems unlikely, for "scientific" disinfectant, we use soap and hand-wash gel (not bleach!), doesn't work by sticking fingers in a cup, and vitamin-E etc... well you can tell it's a bit of joke on my part. BTW I'm suddenly curious how it feels when a finger coated with hand-wash gel (which is mostly alcohol) probes a pussy, it should sting quite a bit.
(1) is possible in real life, but for JAV production, I tend to doubt it. JAV production tend to emphasize showing not actually making sexual pleasure (or pain/discomfort/humiliation/...). It's even a meme that male ejaculations are often fake. So if director wants more convincing orgasm/pain footage he will focus on acting, camera angle, sounds, editing, not border to actually cause pleasure/pain. OTOH, if say soaking finger in ice-cold water before probing is a thing, it would be shown in the scene, not just to show on Twitter.
And for lubs, well we all know Japan love sake and lubs, so same factor: if it's lubs why not show it in scene?
So my best guess is warm water, so the female performer will experience
less discomfort when probed. I'd give this answer...hmmm 15% confidence.
