buffy/faith.
You don't need to explain now. But you do need to explain someday. Okay? And that somewhere there is a grumpy 13 year old Giles. Does he wear glasses still? Does he still do that cleaning thing?
I'm also getting since you filtered that Xander doesn't know? And am I also getting you'd rather he didn't? Since he'd react way less well and probably try to stake Angel again or something?