Deny it all you want but soulmates are real. At least in the wizarding world they are. Connected by an invisible string in their hearts, experiencing the pain of their soulmates in their chest, almost as their own. James has always been in love with the idea of meeting his soulmate. He sees how happy his parents are and can't wait to find that one day. His heart always had the occasional light pain but there were times where his heart ached to the point he couldn't focus on anything else. His heart ached for his soulmate, literally. Suddenly during his second year for a brief period of time, the pain stopped. He worried for his soulmate but also felt a slight reassurance they were not being harmed anymore. During Christmas break, the pain returned. He spent most of Christmas crying in his bed from the pain. If this was even a portion of what his soulmate felt well, that just made James want to find them even more. This pattern continued for a couple years. When Sirius ran away to his house he was so focused on Sirius he didn't even feel the amount of pain his soulmate was experiencing. It only got worse from then on. His heart is constantly aching, desperate to find his soulmate.
Until one night in his 7th and final year, he and the marauders pulling one final prank before they go off and join the order. James was walking under his invisibility cloak preparing for the prank when he heard voices in the distance. These voices were familiar and arguing about something. “I think you need to learn your lesson.” The first voice spat out. James curiously rounded the corner remaining unseen underneath his cloak. He feels a sharp pain at the same time the unidentified man calls out a spell. He briefly thinks that the spell was shot at him but looks up at the sound of someone groaning in pain. A head of tamed jet black curled hair hangs down on his knees in pain. When the man looks up he's met with those piercing silver eyes he so often dreams about. Regulus is the one the spell was shot at. Oh. Oh. Regulus is his soulmate. His soulmate is crumpled on the ground in pain. He sends a silent spell at the attacker causing him to run away. Regulus, still crumpled on the ground, doesn't notice James removing his cloak and walking over. He stretches out to who he now knows is his soulmate. Regulus reluctantly takes it. “What are you doing out here Potter?” Regulus asks, dusting off his pants. “I suppose I could ask you the same thing.” James replied with a smirk visible on his face. Reglus’ eyebrows slightly raise as he nods. “Let me walk you back to your common room.” James says, unable to get rid of the giddy feeling that Regulus Black is his soulmate. His Reggie. “I feel I'm not getting rid of you anyways.” He replies not even sparing him a glance as he starts making his way back to the common room. “So,” James starts as an attempt to fill the silence, “do you know your soulmate yet?” That stops Regulus in his tracks. James looks back confused. “I don't think I have one.” Regulus says quietly. A side of him he's never seen before. “Why not?” James says daring to step closer to him. “I’ve never felt anything in my heart to even signal that they're there.” James looks back and realizes the amount of pain he's been in his whole life would barely be enough to signal to Regulus he was there. They continue walking as James tries to think of something to say. He thinks he should just come out and tell Regulus that they are soulmates. He's about to when “This is my stop.” Regulus says breaking the silence. Before James has the chance to even say anything Regulus is walking into the common room, as he's shutting the door “Regulus,” James said pausing as Regulus looks at him with his eyebrows scrunched, the words sitting on his tongue “have a goodnight.” he smiles. “You too, James.” he says with what James thinks could be a hint of a smile. They keep eye contact the whole time Regulus shuts the door. That's the last time they spoke.
Three months later James is sitting in an order meeting when he gets a small pain in his chest. He thinks nothing of it. Then the pain gets sharper and grabs his chest. Everyone is now looking at him “You alright Prongs?” Sirius asked, concerned. James cries out in pain as Remus and Sirius assist him out of the room laying him down on the couch. James puts his hands over his heart crying out, unable to form words. “Pads, I think it may be his soulmate.” Remus glances over to Sirius concerned. Just as the pain got worse, it stopped. It was gone. James knew what this meant. Regulus is gone. He starts sobbing slowly but not from pain. He slides onto the floor as he starts to hyperventilate Remus and Sirius hold him. He grips their arms as hard as he can, desperate to cling onto reality. Regulus isn't breathing, and at this moment neither is James Potter.