The End of the World. They say that a lot, but this time it really might be. Willow's chest is tight with fear, but she's used to that. No demon is scarier than the SATs. No damnation worse than failure.
The circle is prepared now. The real work of the ritual about to begin. Buffy and Faith aren't back yet. Assuming they're even still alive.
Willow and Giles are alone in the library.
At a sudden impulse (if two years can be called 'sudden') Willow leans in and gives Giles a quick peck on the lips before stepping back from the circle.
Giles blinks, clearly stunned. Willow blushes. He opens his mouth, but what is there to say? He gives a sort of general nod of acknowledgment and then gets on with the chanting.
The world doesn't end. In the days that follow, they share an awkward moment or two when it seems as if one of them might broach the subject of that kiss and what it meant. But time passes.
Willow and Oz are Willow and Oz. And Giles is a much, much older man. Anything incompatible with those realities will just have to wait for another Apocalypse.