Warnings: voyeurism, angst, wanking
Remus finds the mirror in an out-of-the-way storage room on the sixth floor. It's just as he remembers it from his own school days, temptation rolling off it in waves as it sings its siren's song. What he wants will be reflected back at him… his heart's deepest desire.
It's been so long since he felt desire for anything, burning passion having been locked away with a prisoner in Azkaban—a prisoner, he hears, that has just recently escaped. For all the evil that Sirius has done, Remus still longs to set eyes upon that face. To touch, to kiss, to feel alive in a way that only Sirius could make him feel. And with that longing, Remus approaches the mirror.
Just steps before the glass, a figure manifests itself within it. He would know that outline anywhere, and it makes his heart beat faster. But when shadow turns to flesh, his heart pangs. There he is, just as Remus remembers him. His face is youthful, chiseled to fine perfection, unlike the drawn waxen face of that man in the Prophet. So overcome with feelings long since buried, Remus reaches out to touch the glass, to allow his fingertips to meet those of the Erised Sirius.
"I miss you so much," he whispers.
As if in response, Sirius turns to Remus' Erised reflection, winds his arms around him, and kisses him full on the lips. His reflection opens his mouth eagerly for Sirius, their tongues meeting, and Remus can almost feel the ghost of Sirius' lips against his own. It's been so long since he's been kissed like that, so long since he's seen Sirius' lithe and lean body with his eyes, and Remus finds himself reacting physically to the lovers' display in front of him.
Remus' reflection's hand roam over Sirius' body as tongues tangle, the button's of Sirius' shirt but a memory in Remus' wake. Sirius shrugs out of the button-up, and reflection Remus runs his hands over Sirius' ivory chest. Remus remembers the feel of that skin, the taste of it, the trail of dark hair that begins beneath Sirius' navel. His reflection smoothes one finger over the hair before unzipping Sirius' trousers.
Sirius allows his head to drop back—beautiful, long hair brushing against his shoulder blades—as Remus' reflection draws out his length and falls to his knees. It's painful to watch himself and Sirius, but for all that he wants to, Remus can't look away from the display—his lips wrapped around Sirius' cock, Sirius' fingers carding through his hair.
Remus' skin hums pleasantly as it always did under Sirius' touch, as if somehow Sirius is here with him. He fumbles with his robes and trousers, quickly seeking out his own hard length. He strokes as he watches his reflection blow Sirius to completion. And as Sirius' mouth falls open, his brow furrowed, Remus comes with him, as if there is nothing more in the world he desired.