Training
He's seen her train in moonlight.
She can detect the smallest droplets of water.
Now their training is more personal.
She can focus on his chakra, finding precise points to drive him crazy.
She may tease that she has the advantage in the night with Byakuugan but that's not true.
Because he can smell as her desire progresses and hear the slightest little hitch in her breath that tells him what he needs to know.
Perfecting new skills requires constant training they tell each other breathlessly.
Yep.
Even though they're not his students, they laugh that Gai-Sensei would be proud.