Pretty Erotic Nurse

Apparently he gonna marry the nurse, too! The photographer sounds like a solid wingman.

Nana-chan definitely has a red-hot lewd streak.
It makes her vulnerable to assertive rogues like
Sakata, who perceptively notes:
"From my experience, Nana-chan's the type who
just needs a little pressure for her to happily let
you bang her."
(page 4, panel 2)

(Note how quickly & happily Nana-chan submits
to being "spit-roasted" by two men she just met.
She has an extremely lewd streak, bless her hot,
horny little heart.)

Now that you mention that, it's quite possible that, as a result of his occupation and the hazards that apparently come with it, Sakata-san might have dropped certain inhibitions in his behavior that Kubo-san might still be clinging to even unconsciously; perhaps Sakata operates on the premise that "I Only Live Once, so I might as well go all out while I'm here (or something like that)"