He felt like Nabokov, a literary reference that undoubtedly not a single student would get in this day, age and, of course, culture. Wizards who denied any worth to Muggle literature often lost out on the best and worst that mankind had to offer, from bad self-help books to Tolstoy and Neil Gaiman. Being a wizard and a werewolf with little to no employment, public libraries were Remus Lupin's haven during the worst of times, and Muggle books often saw him through the best of times as well.
Right now, Hogwarts combined both of those things. His affection for James' son was slowly turning to something dark, every time he saw a flash of pale skin when the object of his affections rolled up sleeves to cast a particularly difficult charm or countercurse. He almost bit through his lip the day Harry had loosened his tie completely, and undone the top button of his shirt. Too young, but the potential, gods, the potential.
James would have loved to see the boy, strong and independent even at the tender age of thirteen. Lupin had Harry in his office regularly now, alone with the boy and a boggart, casting the image of James' animagus around the room, reminding him why he absolutely had to keep his mind, his hands and his traitorous heart all to himself. He often masturbated furiously both before and after the sessions.
He'd had to add the prequel the day he'd been trying to show Harry the wand movements for a proper Patronus, and ended up pressed up against the boy's back, moving his arm. "Professor, your wand is poking me!" Harry had protested, and Lupin had moved back, shocked at himself. They'd both gone a bit quiet moments later, when Harry's eyes had found Lupin's wand lying on his desk where he'd left it.
"All right, Harry, that will be enough for today," said Lupin briskly, trying to hide the unnatural flush of his cheeks, grateful for his ill-fitting robes and their ability to hide so very, very many sins. His habitual dishabille served only to protect him at times like this, and so many others, when he'd wanted only to go unnoticed. Eyes slid over a man who looked like he might beg for a coin or two, minds promptly filing him in the trash bin as unimportant, insignificant. Unworthy of note.
He'd managed to keep his body under control during their private lessons since then, but tonight would be the real test of his resolve. On the verge of a full moon, with Harry once again having problems with the hand motion. He himself had learned only through painstaking trial-and-error, and it hurt his stomach a bit to think of how much it must've cost Harry to ask, again, to be shown from behind.
He was already half-hard, and the boy wasn't even here yet. Gods preserve him, if he didn't get fired for being a werewolf, he'd certainly be fired if anyone ever got any inkling of this desperate, inappropriate lust. "Professor, I'm ready!" said Harry cheerfully, walking in the door. His robes were slightly askew, hair mussed as James' had always been, tie completely abandoned and collar undone two buttons.
His eyes were bright and sparkling, Lily's eyes in James' face, and Lupin was flooded with memories of their adventures as the Marauders, of looking forward to nights like these in his later school years. Of the first time James had caught him furiously wanking one night in their third year, right before a full moon, when his skin felt too tight and hot to hold his feelings inside. Just like it felt now.
Harry licked his lips, much as James had, and said, "Professor, are you alright?"
Lupin closed his eyes, and shook his head numbly. He was definitely, absolutely, not all right. He was very, very wrong.