Regulus knew what had to be done.
James was getting too attached, and so was he. The war was getting more serious, and Regulus's parents were pushing for him to get the Dark Mark. He had to protect James, and there was only one way to do it.
"Obliviate"
James woke the morning after feeling like his heart has been wrenched out of his chest and someone else is holding it, with gentle hands as blood drips down from the slow pumping heart, then this person taking his heart and locking it deep away where nobody can get to it, and James is left with a gaping wound in his chest, ribs cracked and flesh mangled as if his heart was not taken kindly, but ripped out like a starving animal had take him for prey, and the feeling of a heart of a stranger's in his hands, a heart that doesn't want to be there, a heart that wishes it never met James so it wouldn't feel this gut wrenching loss of having the hands that hold it, with such a caring touch, no longer remembering its owner. Regulus knows it's his fault that James wanders around the corridors of Hogwarts with an empty look in his eyes, that he no longer laughs like he used to, that the beautiful, soft smile that was saved only for Regulus would never grace his features again, but his heart that is no longer his own does not know this. His heart, though he doesn't own it anymore, feels a sadness that makes it pump out blood like it is trying to save a life, but nobody knows who's life it's trying to save. James doesn't know whose heart he holds in his hands, but something deep in his memory tells him to cherish this heart, to protect it with his life. He tries desperately to dig out the memory that makes him feel like this, like something horrible but so, so beautiful, is missing from him, but his efforts only leave him with bloody, torn hands, and his mind strewn across the floor. Tears fall down his cheeks, painting his face with the memories he can't find of a lost lover, ripped away from him by an unknown force. Regulus finds him on the edge of the astronomy tower, ready to follow his lover into death because that is surely where he is, for James can feel the love for this stranger deep within his weary bones, and knows that he would never let him go, but he's gone, and so he must be dead. James is prepared to follow a faceless stranger into the cruel, icy hands of Death. He doesn't feel scared, only peaceful. Regulus runs, screaming out James' name, but he is a second too late. His fingers brush the edge of James's jacket, trying desperately to grab on, but as James turns to meet him, all he does is smile that special smile, the shy, loving one that he only uses for Regulus, reaches out a hand, as if asking for his heart back, and steps back. He keeps that smile on his face right to the end, and in his last moments, he hears a scream so devastating, so heartbroken, the power of it nearly kills James all on its own. His body cracks sickeningly against the stone floor, blood that is not his own, but surely his lover's, leaking out, staining the floor a deep red. Death comes kindly now, no longer cruel and cold, but a soft, loving hand reaching for his own. James takes it, knowing he will finally meet the keeper of his heart. But, nobody is waiting for him after death. He is all alone again. He waits patiently for nearly two years, until finally, in 1979, a kind, familiar hand wakes him from his slumber. Even before opening his eyes, James knows who woke him. He feels memory after memory hit him with a force so powerful it leaves him breathless.
"Hello, hello, are you lonely?"
James gasps softly, finally being able to hear his lover's voice.
"I'm sorry it's just the chemicals"
He can feel the tears sliding down his face, washing away the blood.
"Hello, hello, do you know me?"
"I would know you anywhere my love, even in death"