The first time Lily says it, she's deathly serious. They're sitting in Potions, and Professor Slughorn has just finished lecturing them on the importance of timing, and all she can think about is the fact that they wouldn't have ruined their potion if Regulus had been able to put aside his blood prejudice for long enough to simply talk to her.
"For the record, I blame you," she mutters under her breath as Slughorn walks back to the front of the room. She knows it's childish, but it's true, and he's probably said far worse about her in the past.
Regulus winces, and she hopes it's because he realises that he's at fault, not because he's repulsed by the idea of her daring to speak in his presence.
The one good thing about the situation is that Slughorn is unlikely to pair them up again. They're both usually near the top of their cohort, so she figures that he won't want to risk their marks dropping in his class in particular.
She's wrong. A few lessons later, he pairs them up again, and she resigns herself to either doing all the work by herself or getting another failing mark.
But she's wrong about that, too. Perhaps the wince was because Regulus realised it was his fault after all. Whatever the reason, all she knows is that he seems to be willing to talk to her this time. He's far from chatty, but he's communicative, and that's enough for them to successfully complete the potion before most of their classmates.
-x-
The first time Regulus says it, he's only half-serious. Death Eaters – his relatives and former friends among them – are closing in on the Order, and they're standing in the centre of it, their wands held tightly in their white-knuckled fists. They've come a long way in the years since that first Potions lesson; instead of frustration or anger, his voice is laced with concern that, Lily knows, extends to her wellbeing as well.
"For the record," he says, "I blame you."
Even though she's just as scared, she rolls her eyes. She was the one who finally convinced him to defect to the Order, true, but she wouldn't have had the slightest chance of doing so if it weren't for his house-elf. "Come on, Reg. Most of it was Kreacher's doing, not mine."
He laughs, but the sound is hollow and shaky. "Yes, but he's still trying to wrap his head around the concept of sarcasm, so I can't exactly go around saying it to him, now, can I?"
Her face scrunches up as she thinks of the punishments the house-elf would try to inflict on himself if either of them ever said that to him. But before she can say anything, a purple spell soars through the air between their heads, and the fight begins. For the next few hours, all she knows is flashing colours and rapid movements and pounding hearts and burning lungs. There's no time for strategy. Everything is chaos, and it's all she can do to keep up with it.
Somehow, when the dust settles, they are the ones who are still standing. She feels like she's aged ten years, and his eyes look like he has. At first, she's worried that he might be second-guessing his decision to switch sides. She knows he regrets ever having bought into his family's lies, but it can't have been easy to face people he grew up with and know that they were trying to kill him.
But all he says is, "Let's go home."
He reaches out, and she takes his hand, and she can feel the cool metal of his wedding band against her skin. She smiles wearily. She knows they need to talk about the emotional fallout of the battle at some point, but the conversation will keep. For now, she wants nothing more than to sleep for a week.
After that, they'll talk.
A/N: For Amber (Cheeky Slytherin Lass) for the Drabble Game Challenge. Prompts: Regulus/Lily; "For the record, I blame you."