HANZO IS SO GULLIBLE I LOVE IT
Mercy can ask him anything and he’ll just nod and go along because he doesn’t want to come across like he doesn’t want to inquire further. So he lets her fondle his tits and massage his prostate and, yes, sound his pretty cock without a word of complaint.
Eyes going big and mouth dropping open as he watches her slowly lowering one stainless steel rod into his urethra. He panics a little (a lot) because it feels strange and different but Mercy can be very no-nonsense if she wants to.
(I also like the thought of him doing it to himself, though. Secretly in the middle of the night, sounding himself in his bed, being very quiet so nobody will hear how he’s jerking it after sounding himself until his piss hole burns a little from it.)