Regulus Black was the boy you knew you would never really be able to have, but you loved him anyway. Throughout all of your years at Hogwarts, your romance would have always been a forbidden one. You met and spoke a little on your first train ride to Hogwarts together, but when your arrived at the school, you were sorted into Hufflepuff and he into Slytherin. You learned early on that Hufflepuffs and Slytherins don't normally mix; in fact, Slytherins don't normally mix with anyone outside their own house. 

 In your early school years, you tried to be friends with Regulus in secret, which didn't work out too badly back then. But as you got into your teenage years, you found yourself wanting more than that. You wanted something romantic, and so did he. But that also had to be done in secret, and that felt like an even worse secret than just being friends. As the years went on, you saw less and less of Regulus, which was the opposite of what you wanted. 

 By the time you both graduated from Hogwarts, Regulus had fully committed himself to Lord Voldemort and joined him as a Death Eater. It wasn't a life you would ever be able to commit to, and once he leaves to do Voldemort's work, you know there's a chance you might never see him again. 

 You don't hear from Regulus for a long time after that, but you don't give up the hope that you'll hear something of him. You don't know how to contact him, and you don't know who to reach out to for news of him; no one knows of your love but you two, and you can't imagine any of his family and friends reacting positively to that news. 

 One day, after a long time of waiting, you receive a letter addressed to you in Regulus' handwriting. Excited and curious, you immediately tear the envelope open and pull out the letter folded up inside. 

My dear Y/N, 

 I'm sorry I cannot see you in person one last time, but I'm afraid that a goodbye like that would be too much for both of us. 

 I have left Voldemort. I want nothing to do with him, his Death Eaters or any of their plans anymore. I never should have joined him in the first place, and that is something I now regret. However, rather than Voldemort hunting me down and killing me for deserting him, I still have one chance to do something right. 

 Voldemort has seven horcruxes, of which his life is tied to. I know the location of one of them, and have had a fake one made. My plan is to go there and replace the real one with the fake. The real one shall be destroyed as soon as possible, but it is most likely that I will not survive. 

 I am sorry that I have to leave you like this, Y/N, but I have to do this, even if it means sacrificing myself. It will be worth it to make a start on defeating Voldemort. You know I love you, and I hope you will find happiness in your life once I'm gone. 

                                                                                                           Yours, 
                                                                                                           Regulus

 You read this letter over and over again, but nothing changes. Regulus is gone. He isn't coming back for you, and he never will. But he learned his mistake, and he did his best to make it right again. No one else close to him would have appreciated the sacrifice, but you know the enormity of it because you knew his heart in a way no one else seemed to. 

 You keep the letter, leaving it safely tucked away in drawer. Someone needs to remember Regulus Black as a hero, so it will have to be you.