A/N: As we all know, Regulus Arcturus Black was never "just evil". I think many things contributed to his eventual change of heart (Voldemort's treatment of Kreacher being the last straw), and this is a story about one of these reasons: his relationship with a blood traitor from Hufflepuff. It will be a multi-chaptered fic but not a very long one. I hope you'll enjoy it. Reviews will be much appreciated!

Disclaimer: I do not own Harry Potter.

One of the Reasons

1. The Girl

It was a cold Saturday afternoon in early January and Regulus Black had just finished his Quidditch practice. Although he was dead tired and longed for bed, he took a quick shower and trudged to the library. He had been given a lot of essays for homework this week and somehow they never wanted to write themselves. (And the fact that he was a Slytherin didn't necessarily mean he was content with low grades. Or detentions, for that matter.) But there was an upside to this situation which made it a lot more enjoyable and it was the high probability of seeing The Girl.

He must have seen her before but he hadn't really noticed her till this year. He walked into the library on one of the first days of school and – bam! – there she was. He didn't know what it was that caught his attention. Why he suddenly saw her in a different way than any other girl before. She was quite ordinary, there was nothing mysterious or exceedingly beautiful about her, and she definitely wasn't the loud type who would do anything to get into the spotlight. But somehow she stood apart from all the other girls in Hogwarts.

He didn't know much about her; only what he observed during his studying in the library. He noticed for example that she always wore red trainers and a carved wooden bangle around her left wrist, and that she was energetic and high-spirited. Usually she let her chestnut hair fall freely onto her shoulders but sometimes she pulled it into a ponytail, allowing him to admire her long graceful neck. Most of the time she studied with a group of friends and it looked like she was really helpful and patient when explaining things. When she was bored, she often levitated her quill or charmed her inkpot to do backflips. She obeyed most of the library rules, though he saw her smuggling in biscuits a couple of times. Oh, and she was a Hufflepuff but he was trying not to think about it.

The first thing he did after entering the library that evening was to look around for her but she wasn't there yet. His favourite table near the window was occupied so he took another seat and waited impatiently for The Girl to appear. Finally she came in with a group of friends and they all sat at a nearby table. He had a very good view of her now and could see the twinkle in her eyes when she smiled. She seemed especially perky that evening, and he couldn't take his eyes off her. But he tried really hard to do some work, too. His essay on Vanishing big mammals was due on Monday, after all.

After an hour he went to fetch a book he thought might come in useful (How To Vanish An Elephant In Three Easy Steps) and when he came back, there was a note lying on top of his essay. Somebody (and he had a pretty good idea who it was) had written in clear handwriting: Stop staring. It's annoying.

So apparently he wasn't as stealthy as he thought. He only hoped nobody else had noticed or he could be in trouble with his mates. The Girl was a Hufflepuff, after all, so she was technically off-limits to him.

This was the moment when he should have used his head for more than something to keep his ears apart and let the whole matter drop. It was not too late, nothing incriminating had happened, nobody knew he had a thing for a Hufflepuff girl. He had only to walk away and stop thinking about her, nothing more. But he didn't. For once he didn't listen to the voice in his head that always told him to stay out of trouble and do only what was expected of him. He just threw all caution to the wind and jumped at the opportunity to establish contact. True, he couldn't see RSVP written anywhere but he could always argue he felt he should answer the note out of sheer politeness. And it was the only way to fix her bad first impression of him: he didn't want her to think he was a creep or a jerk. So he took a deep breath, wrote "I'm sorry" on another piece of parchment and slipped it into her bag on his way out.

He passed her in the corridor the next morning and was quite sure she eyed him thoughtfully. But when he entered the library that evening, she did not acknowledge his presence in any way and he was baffled. Did he come across as a creepy stalker, then? Maybe he should have added something about not being able to stop looking at her beautiful eyes/hair/smile? But wouldn't that be too cheesy? After all, he just wanted to get acquainted, not profess undying love to her. But maybe he didn't make his intentions clear? He had to admit "I'm sorry" meant something a little different than "I want to know you". But then, girls were supposed to be good at reading between the lines, right?

He couldn't concentrate on his work and kept glancing at her every few seconds. Once or twice their eyes met but she quickly dropped her gaze. As there were no signs of flirting on her part, he guessed she still found him annoying. After an hour she stood up and he quickly started leafing through one of his books to appear busy. He thought she was looking for something on the shelves and was therefore surprised when she came up to his desk.

"I'm sorry, is there a problem?" she asked, frowning slightly.

"Um… No, why?"

"Well, you keep staring at me as if I had something on my face, so I just wondered if there was something wrong," she replied frigidly. She didn't seem at all apprehensive about addressing an older Slytherin.

"There's nothing wrong with your face," he said the first thing that popped into his head. She didn't smile at the dubious compliment.

"No, but there's something wrong with my blood, eh?" she replied scathingly and turned away. He quickly caught her wrist to stop her.

"I don't even know your blood status. And–" He wanted to add that he didn't care about it but she cut him off.

"Well, by your standards, I'm a blood traitor," she said proudly, as if challenging him to curse her. Then she whipped out her wand and used a Revulsion Jinx to make him let go of her hand.

"Ow!"

"No magic in the library, young lady!" Madam Pince was upon them within seconds.

The Girl apologized stiffly and went back to her table. Regulus rubbed his hand and grimaced. He couldn't believe his rotten luck. Not only was she a blood traitor from Hufflepuff, but she also thought he was a Death Eater on the prowl to kill people like her. Well, he couldn't really blame her, though it really complicated everything. But he admired her pluck and this incident only made him more determined to get to know her.