Butterfly kisses against the other's cheeks.
6O sat on the bed of her own room, she had invited 21O to come over after her duty was done, so she could show her something she found in the database.
So they both sat, with the Operator with braids having one arm around the other, while her free one was displaying things on a screen.
She showed 21O pages of an old book she found in the YoRHa database, apparently about some colorful insects.
She knew the other blonde was interested in old world information, but really she just wanted an excuse to be with her, and sit next to each other and cuddle her a bit.
Things were rough enough as they were, so 6O made it her mission to make them less hard for them.
Apparently the insects on screen that were of all kinds of colors were called butterflies.
A name not all unknown to 6O though.
She once read about types of kisses humans used to give to their partners, for research purposes of course.
It was just very convenient that she was just lying her head on 21O's shoulder and they both weren't wearing their respective veils, discarded and forgotten on a corner of the bed…
"You are tickling me…" a little blush appeared on 21O's face, as 6O decided to lightly brush her eyelashes against her cheek.
For some reason…
"They're called butterfly kisses." 6O just replied with a smile. "You don't like them?"
It wasn't that she didn't like them… it was just… weird?
But it was still an affectionate gesture…
"Please, continue…" 21O's green eyes looked away, embarrassed.
She just could not say no to 6O.