Because who doesn't love a good Nightbird AU?

Kurt stumbled at the first tremor. At the time, he assumed it was just from the subway rumbling underneath them and accepted Blaine's steadying arm with a kiss to the cheek before continuing their conversation as normal.

The second tremor, however, caused an explosion a few blocks away, making them and the other pedestrians stop and stare in horror. Kurt would have likely stayed frozen for a while, but Blaine - who clearly had a death wish - started running toward the calamity.

"Blaine!" Kurt yelled, beginning to run after his boyfriend. "Blaine!"

Blaine didn't slow down. If anything, he ran faster, making Kurt have to focus on keeping up with him.

When the hell did he learn to run like this? Kurt thought, gasping for air. He didn't manage to catch up to Blaine before they reached the explosion site, where two burly men were hovering in mid-air and taunting the crowd. Kurt had to bend down and rest his forearms against his thighs to catch his breath as he listened to them, noting that Blaine was somehow still upright and breathing normally out of the corner of his eye.

"Here, birdie birdie birdie!"

"Come and get us! Or are you afraid of a couple of cat burglars?"

"Maybe Nightbird's flown the coop."

"Or maybe he knows that there's no stopping the Titans. Soon we'll be running this city!"

The two men high-fived, making a noise like a thunderclap as they connected. Most of the crowd watching them flinched and covered their ears, but Kurt saw Blaine begin to run again out of the corner of his eye.

"Really?" Kurt said, instantly following.

He chased Blaine down a web of streets, almost losing him a few times when he started running out of breath. Thankfully, Blaine's hair tended to gleam in the sunlight, making it easy for Kurt to relocate him and keep trying to catch up.

"Blaine! Where are you going?" Kurt yelled when he thought he was close enough, but Blaine didn't even hesitate. Instead, he ducked down an alleyway in between a pastry shop and an abandoned storefront.

Kurt had no choice but to follow. He slowed as he saw Blaine input a sequence of digits into a keypad, then open a door into the basement of the pastry shop and disappear.

"What?" Kurt said softly, crinkling his forehead. He knew of the pastry shop they were at - Blaine loved their cronuts, though Kurt thought they were a bit too dry - but Blaine had never mentioned knowing the access code to the basement, nor was there any reason Kurt could think of that Blaine would need to.

Kurt walked over to the keypad and looked at it, trying to look for worn buttons and remember what Blaine had punched in. A faded "5" and a vague recollection of Blaine's motions made Kurt try entering the first four digits of his own birthday, which resulted in a green light and the sound of a lock opening.

"Well. Here goes nothing," Kurt said, and opened the door.

He wasn't ready for the sight that greeted him once he entered the shop. The space was mostly dark except for the various computer screens lighting the far wall, one of which was showing two blinking red lights over the site of the explosion. Kurt stared for a moment, entranced, then started looking around for Blaine.

He had on a red polo and jeans, Kurt thought, trying to find a flash of either of those colors anywhere. He located Blaine's shirt in a pile on the ground in the far left corner after a quick scan, trailing his eyes upward to discover-

"Nightbird?"

"Kurt! How did you get in here?"

"Wait, you know my name?" Kurt asked, squinting. He started walking over to Nightbird, who tried to shrink back into the wall. Once Kurt got close enough, he only needed to look into Nightbird's eyes to know. "Blaine?!"

"I - uh-"

"Holy shit. Holy shit, how is this real?" Kurt said, pressing his right hand to his temple. "Am I hallucinating? Is this actually all because I passed out when the explosion hit?"

"I promise, you're awake," Blaine said. He reached out to squeeze Kurt's elbow. "And I'll explain everything later. But right now, there are two bad guys with superpowers who are looking for me."

"Yeah. Yeah, go," Kurt said, feeling a little faint. "But I swear to God, if you don't come back in one piece, I'll kill you myself."

Blaine smiled crookedly and laughed, sounding relieved. "I'll always come back to you."

Kurt reached up and squeezed Blaine's hand as Blaine caressed his elbow one last time, then watched as Blaine bolted out the door, catching a second of Blaine's lift-off before the metal slammed back into place.

"God," Kurt said breathlessly. He looked around for a seat, then collapsed into the swivel chair in front of the bay of monitors, letting out a deep, loud breath. "I can't believe this."

He felt his mind go into overdrive as he tried to process everything he had just learned, idly staring at the blue blip that had to represent Blaine move closer and closer to the red dots. While he was mostly relieved that Blaine's late night disappearances and flaky excuses for missing dates now had a great explanation, he couldn't stop being displeased by one detail of their last conversation, no matter how much he tried to distract himself by exploring the Bird's Nest (as the media called it). He was still stuck on this detail when Blaine finally arrived back, a little bruised and sweaty but not heavily injured, as far as Kurt could tell.

"Kurt?"

"You didn't kiss me goodbye."

"What?" Blaine asked, dropping his mask on the ground.

"You left to go fight two huge supervillains and didn't kiss me goodbye. That could've been the last time we ever saw each other, Blaine, why the fuck didn't you-"

"Because I thought you might not want me to!" Blaine interrupted, stunning Kurt into silence. "I know you said you wanted me to come back in one piece, but that's not the same as wanting me as your boyfriend after finding out I've been keeping this huge secret from you."

"Blaine, if I'd been that mad, you would've been well aware of it before you left to get those morons," Kurt said, raising an eyebrow. "Do I wish you'd actually told me? Of course. But I'm still relieved to find out that your weird disappearances aren't because you're cheating on me. And on top of that, I'm proud."

"You're proud?" Blaine asked quietly, a shy look on his face.

"B, you've been saving New York basically by yourself for months now. You've never backed down from a fight, and you've kept us all safe. I can't say I won't be scared whenever you run off now, but I'm so amazingly proud of you for using your abilities to protect the city instead of just hiding them away."

"I would've protected Lima had I had powers when we were in high school," Blaine said. "I only got my abilities after a bit of an incident at orientation last semester."

"You're going to have to tell me all about that. But maybe not here?" Kurt said, getting out of his chair and walking over to Blaine. "I want to go home."

"Me too. But first," Blaine said before leaning in and kissing Kurt thoroughly, wrapping his arms around his waist to bring Kurt in close. "That's to make up for earlier. If we're together next time something attacks the city, I promise I won't leave without kissing you goodbye."

Kurt blinked woozily for a moment before saying, "We're going to be together every time, because I'm going to be here in the Nest manning these computers from now on. There's not a chance in hell of me leaving you to defend the city by yourself now that I know."

"Kurt-"

"Shh. No arguments," Kurt said, shooting Blaine a strict glare. "I know I can't fight off anyone with superpowers, but I can monitor the situation from here and try to give you advice. Plus, someone needs to know where you might be if you don't make it back sometime."

"I have some provisions in place for that, but I can tell you're not going to compromise on this one," Blaine said. With a slight grin, he continued, "Good thing there's no one else I'd rather have watching my back."

"You're looking out for the whole city. The least I can do is look out for you in return."

Kurt pulled Blaine in for another kiss to punctuate that statement, making a loud "mwah!" noise as they broke apart.

"You know," Blaine said, smirking. "We'll have to get you a codename now, too. Any ideas?"

"I'll know it when I hear it," Kurt said, trying to think.

Blaine ensured that he heard plenty of options, both good and bad, all the way home.