Sirius observes his sleeping lover one last time.
He runs a thumb over his every feature: his nose, his eyes, his lips…
He leans in and kisses him once more, and in his sleep Remus responds, as though his sleeping self knows that, in moments, it will end, and Sirius will be gone.
The moment ends. Remus sleeps on, and Sirius escapes the house as quietly as possible.
And despite his promises to himself that he won't come back the next night, he is assured he will.
Remus wakes, finds him gone, and tries desperately to hold back his tears.