Written for the One Hour Challenge although I didn't finish within the time limit exactly… I was given Minerva/Regulus as a pairing. Weird.
Minerva tapped her wand against her desk while she watched her students fail miserably to turn an empty coffee mug into a candlestick. She loved her job, but the beginning of the school year was frustrating for her. She couldn't wait until after the holidays when she could actually see her students' improvement. For now, though, she would have to walk around her classroom and perhaps see one correctly transfigured candlestick on a desk.
She decided it was best to stop tapping her wand, as she tended to set things on fire when she did that out of frustration. She got up and made her rounds, weaving through the desks of Hufflepuffs and Slytherins, every once in a while calling out suggestions.
"You need to speak more clearly, Mr. Nott."
"Why are you pointing your wand at your neighbor and not at your coffee mug, Miss Perkins?"
"Mr. Black, please, do wake up."
Regulus immediately sat up in his seat, a red mark on his forehead where he'd been resting it on the desk. He rubbed the sleep from his eyes and met Minerva's glare. He was much less defiant than his brother, she observed, but she absolutely hated when students slept in class. So she did the only logical thing to do.
"Detention, Mr. Black. My office on Monday at 8pm."
Regulus grabbed his wand and nodded before setting to work on his coffee mug. Little did Minerva know, Monday detentions would be a weekly thing from that point on. If you asked either of them now, they probably wouldn't be able to tell you who had started it.
Maybe it was that Minerva was intrigued by the difference between the quiet Regulus and the obnoxious Sirius Black. She may have found it refreshing, not to mention that Regulus was just as handsome as his brother without being so vain. She may have given him detention despite the fact that he was the only one succeeding to transfigure anything before falling asleep.
Or maybe Regulus fell asleep in class on purpose because Monday nights in his Professor's office weren't so bad. And she always offered him a biscuit from a tin on her desk for some reason. And he would always accept and say "thank you."
Maybe he wasn't really sleeping at all.
Neither of them would speak what was really on their mind. The hours would go by and Regulus would scribble lines about not sleeping in class, while Minerva would grade papers. Every now and then she would look up and meet his eyes for a split second before he lowered them to his paper. She would look forward to her Mondays because she would have some company while she graded her students' work, or drew up her lesson plans, or wrote letters.
It all changed one week, though. Regulus did not fall asleep in class. He completed his work and he was respectful and Minerva could not think of a reason to give him detention. She was horrified to find that she was disappointed. It was the first pangs of discovery that perhaps she liked this boy a little too much. Why should she be looking for a reason to give him detention? What teacher wants to inflict punishment on a student?
It tormented her all weekend that she could have made a mistake. Maybe this whole time she'd been acting terribly inappropriately without ever realizing it. Did the entire class know that she was attracted to her student? Had she been that obvious to everyone but herself? She relived the last few months in her mind and she found that she really had enjoyed the boy's company, that she looked forward to her Monday nights, that the few moments of conversation between teacher and student, while innocent, were more important to her than she dared say.
Monday night came and she pulled out her assignments that needed to be graded and set to work. It was lonely. She did her best to keep herself from looking up at the empty seat in front of her. But one time she did look up, out of habit she supposed, only to find that the seat was not empty at all. There sat Regulus with his Transfiguration book open, reading quietly.
She jumped in her seat, capturing his attention.
"When did you come in here?"
Regulus shrugged. "A few minutes ago," he said nonchalantly. He turned the page and continued reading.
Minerva stopped him again. "I did not give you detention tonight."
Regulus looked up once more. His face reddened slightly but his expression was passive as he said, "I know."
She should have asked why he came anyway. She should have asked. But she decided it was unnecessary. It would open the conversation up to things that should not be spoken between teacher and student. He understood and silently agreed with her. But every Monday if you looked into Minerva McGonagall's office, you would see Regulus Black in the seat before her, completing a self inflicted detention.
It might be observed that Regulus was a masochist that way. It was an unfortunate family trait. Blacks always seem to fall for those who refuse to reciprocate, for noble reasons or not. And Minerva always fell for those she couldn't have. It was an ironic bit of history that few at the Order of the Phoenix knew about.
Even after all those years and Regulus had grown up and graduated Hogwarts, she still thought about him from time to time. When she heard that he'd become a Death Eater she cried herself to sleep; something she'd never done over any other man. She confided this to Albus who simply smiled and patted her shoulder.
"Death Eaters break my heart too, Minerva," he said. "They know not what they do to us teachers who only wish the best for them; even if the best is a detention or two." He then smiled down at her, eyes twinkling behind his glasses. "Or perhaps many more than just two."