Full summary: Demon!blaine and human!kurt have been dating for quite a while (both out of school) and love each other very deeply but Kurt doesn't know Blaine's not human, and then one day he starts noticing little things, and after all he accidentally finds out somehow and is scared&pissed(&maybe feels a bit betrayed) and Blaine just tries to fix and explain everything and well, he does (duh) Mystery and darkness yet pure and sweet love.

Tweaked slightly, but the gist is still accurate.

In retrospect, it all made sense.

How Blaine was remarkably self-possessed and charming for a fifteen year old when they met.

How Blaine had always loved giving him hickies and wrapping an arm around his waist whenever they went out.

How Blaine's temper could be...explosive, to put it mildly. Kurt still vividly recalled the time Blaine had confronted Karofsky back at McKinley, even though it had been almost five years.

Seeing a tiny, dapper gentleman lay out a hulk like Karofsky in two blows wasn't something he was likely to forget, honestly. Nor was Blaine's expression - enraged, feral, inhuman - ever likely to fade from his mind.

It had taken him, Sam, Finn, and Santana to hold Blaine back that day - how had he not guessed earlier?

"It wasn't an adrenaline rush like the kind mothers who lift cars off their infant children get, moron," Kurt muttered to himself. He sat on the couch, staring down at the floor and trying to process this revelation. "It was because he's a - Blaine's a-"

He couldn't say the last word.

"Blaine's a what?" Blaine asked cheerfully from the doorway, making Kurt jump. "Sorry, honey, didn't mean to scare you."

"Oh, it's fine, B," Kurt said, aiming for a breezy tone. "What do you want for dinner? I'm thinking Thai."

"Yeah, sounds good to me. I'm a what, though?" Blaine said, clearly not acknowledging Kurt's vague attempts at deflection. "You sounded distressed."

"Fine. You want to know what I was going to call you?" Kurt said, letting all his hurt show. "A demon."

Blaine paled.

"How could you not tell me?" Kurt demanded, trying not to cry with anger. "I mean, sure, you didn't have to mention it the day we met, but it's been five years, Blaine! Were you ever going to tell me, or was I just supposed to live in the dark for the rest of our lives? Where's the trust?"

"Kurt, I swear, I've always meant to tell you," Blaine said frantically. "I just didn't know how to bring it up!"

"I dunno, how about 'Hey, Kurt, being gay and part-Asian aren't the only minority statuses I have,'?" Kurt quipped. "Or maybe telling me that it wasn't the boxing lessons you've taken that allowed you to knock out Karofsky - it was the supernatural demon strength."

Blaine tried to walk over to Kurt's spot on the couch, but he flinched away instinctively. Blaine's face crumpled. "I'm sorry, Kurt, I'm so sorry. I waited too long, I know, and now you hate me. I'll leave, if you want, just give me a minute to pack a bag-"

"No," Kurt said, heart shattering in his chest at the thought of Blaine walking out forever, even if he was mad as hell about the deception. "I don't hate you. I don't want you to leave. At least - you wouldn't hurt me or anything, right?"

"I could never," Blaine said, beginning to cry. "Kurt, I love you so much, I could never hurt you. God, this is why I was so afraid to tell you - I never wanted you to be scared of me."

"And I get that, Blaine, but finding out the love of your life isn't technically human is always gonna be a little frightening!" Kurt said. "Especially when you have to find out for yourself after a pointed remark from one of those sycophants at school!"

"What did they say? I'll kill them," Blaine said, face hardening.

Kurt grabbed his arm and pulled him down. "No, you won't, Hellboy. Killing someone just to prove you're not scary wouldn't exactly help your cause!"

"Right, you're right. Sorry," Blaine said. He blew out a long breath before dropping his head into his hands. "This is really not how I was expecting tonight to go."

"You think I saw this coming?" Kurt asked. "Like I woke up this morning and thought, hmm, what do I want to do today? Hit the gym, do some studying, confront my boyfriend about his inhuman nature…."

Blaine giggled wetly. "Well, when you put it like that…."

Kurt couldn't help but laugh along, which quickly turned into both of them having hysterics.

"So you're really okay with all of this?" Blaine asked after they'd collected themselves. "I understand if you need some time to process, and I really can clear out for a while if that'll help."

"I'm not fully there just yet, but I'm not about to run screaming for the hills," Kurt said, taking one of Blaine's hands in both of his. "And I don't want you to leave, either. I think I'd just freak myself out with all sorts of questions and worries if you weren't there to answer them."

"I'll tell you anything you want to know," Blaine said instantly. "That was always part of my plan, if I ever worked up the nerve to implement it."

"Don't think you're off the hook for not telling me, by the way," Kurt said. "I may not be making you leave, but you're sleeping on the couch for like a month now."

"We'll see," Blaine said, smirking. He was probably recalling the last time Kurt said he was going to be on the couch for a month, when he had ended up back in their bed after one and a half evenings - Kurt had woken up cold and lonely the second night and ended the ban in favor of cuddling.

Whatever. Kurt could totally hold out longer for an offense this serious. Blaine would be out here for at least three nights. Probably. If Kurt could find where he'd left Bruce.

"I mean it!" Kurt said stubbornly, ignoring his own doubts. "You can't just lie to me for five years and expect to get off scot-free."

"Have I said I'm sorry enough times yet?" Blaine asked. "Because I still am."

"I'll let you know when I'm tired of hearing it," Kurt said faux-haughtily. "For now...well, I have one major question."

"Go on," Blaine said, mouth quirking in curiosity.

"All the neck kissing...is that like a kink of yours, or some kind of demonic mating ritual?" Kurt teased. "Will it keep away any other demons I might come across on the street?"

"It had better," Blaine said darkly. He focused on Kurt's neck, long and uncovered since he was only wearing a button-down shirt. "You're mine, Kurt."

Well. Kurt wasn't about to let that stand. "Just as long as you remember that you're mine, too," he said, a little breathier than he would've liked - Blaine had started kissing up behind his ear, and he was losing any focus he may have had. "I'm - ungh - not letting you get all alpha male on me now that I know the truth."

"We'll trade off," Blaine offered. "You can let me know when I'm getting too domineering."

"And I suppose I can let you - oh God right there - mark me up occasionally. If that'll keep you from ripping innocent bystanders to shreds if they give me the eye one too many times."

"If? More like when," Blaine said, almost growling. "That guy on the bus yesterday…."

Kurt pulled Blaine's head up so they could kiss properly. "Less talking."

"As you wish," Blaine said, smiling playfully before intensifying his fixation on Kurt's neck.

Blaine didn't end up in their bed that night. But to be fair, neither did Kurt.

Apparently this 'demonic boyfriend' thing may have been more of a boon than Kurt had anticipated.