Remus Lupin lived by the wax and wane of the moon. There was a time when he used to fight against it, try to carry on as usual and keep up appearances. Sometimes, he still did. He tried to resist but more and more he seemed to realise that he was only making the inevitable harder to bear. He preferred the wane, once his body had recovered from the moon. It was when he felt most human, less the victim of unwanted desires and urges.

Sirius Black cared little for the moon. He lived by the wax and wane of Remus Lupin.

After the full moon, there were the calm weeks. First, the recovery. Sirius enjoyed his role as carer, provider. He loved to see the tension leave Remus as Sirius’s hands soothed balm over his overexerted muscles. Next, the boring week. Remus would be mopey and quiet, throwing apologetic looks at Sirius left, right and centre. It was generally not much fun. Then, it started to get interesting.

The restlessness would start after the new moon. It would build, he would fight it, until something snapped. That was the moment Sirius looked forward to. The moment he craved. It was a complicated dance, with Remus trying desperately to hold on to the last vestiges of control. Sirius knew just how to tip him over the edge. It was all about the timing. When the look in his eyes flickered constantly between desperate hunger and frustrated fear. That was the time to quietly slip away and prepare himself.

Remus had grown somewhat accustomed to the routine. He knew what Sirius was up to when he disappeared into the bathroom, and the wolf and man would come to odds. He would wait. Then he would leave. Then he would make an attempt to tear the door down with his bare hands. Then, he would wait.

By the time Sirius stepped out entirely naked — having spent a great deal of time doing nothing at all, just to build the glorious tension — the fear and hesitation were long gone. Hunger, impatience, desire, want reigned supreme. Remus would drag him to their room and throw him on the bed, if he made it that far. Occasionally, it would happen on the floor of the landing, or against the wall right outside the bathroom. Sirius preferred the bed, however, and had mostly perfected his timing so as not to let Remus get worked up too far.

Remus would tear impatiently at his own clothes, sending buttons scattering, leaving shirts irreparable. Sirius would stretch himself out, spread his legs wantonly, expose the soft juncture of his neck fearlessly. Remus would descend, greedy hands and lips and teeth. How Sirius wanted those teeth. At first it had scared him, skating on the thin ice that separated this Remus from sheer ferality. He had feared the bite, feared that Remus’s hunger would tempt him too far, tempt him to feed. It didn’t take long for Sirius to realise that it wasn’t that sort of hunger. It was raw sexual need. The need of the wolf to mark, to claim his mate. And Sirius came to need it, possibly even more than Remus did.

The first bite was always the most intense. Always as Remus slid his thick cock inside, the dance of pain and pleasure and relief, overwhelming. He would lap at it with his tongue, soothing even as he harshly fucked into him. Sirius was helpless. He would lay, and take, and love, and savour and beg for more. That mouth would roam over his skin all the while, lips sucking and trailing and kissing. The bites would come, but they were random, unpredictable, just the way Sirius liked it. Just as he neared his peak, ready to spill as Remus dragged across his prostate on every thrust, the teeth would come, and tear him away from the edge. Prolonged, enhanced. Those were the times that felt right. Trusting, belonging to Remus, completely, unreservedly. Carrying his marks, his scent. From start to end, only one word would leave Remus's lips, like a mantra.

Mine.

The sting, the ache, would dull with time. The marks would disappear, but the wolf would be back.

And Sirius would wait.