"Are you sure Lydia is okay with this?"

"Yeah, man, it's fine." At Derek's doubtful look, Stiles sighed. "Do you really think we're going to spend the rest of our lives only being together when it's all three of us?"

The casual use of the phrase "the rest of our lives" threw Derek for a loop for a moment, and he had to pause to rein in the flash of happiness that speared through him. "I guess not," he admitted, feeling foolish. Gesturing for Stiles to head into the living room, he stepped into the kitchen area for a moment in order to take a deep breath and calm down somewhat. When he felt like he was under control, he grabbed a bottle of wine and a couple glasses and followed Stiles into the living room, sinking down onto the couch beside him.

Stiles snorted. "Really, Derek? Wine? You trying to get me drunk and take advantage of me?"

He made a face at Stiles and set the glasses down with a thunk. "I was trying to be a good host, but if you're going to give me shit, you can just get your own drink," he groused, though it lacked heat.

"Since when are you my host?" Stiles asked, his eyebrows scrunching together in confusion. "I practically lived here back when we were, y'know, together-but-not-together. This might be a new version of us, but it's still us."

The words brought a warmth to Derek's heart that embarrassed him. The whole situation was weird and complicated and still confused him, but for Stiles it was so simple. They were together. All of them. He was still trying to figure out how to adjust and Stiles and Lydia were blithely rolling along, thinking of happily-ever-after as if it were a foregone conclusion. It both awed and scared him. Happily-ever-after wasn't exactly in his wheelhouse. He wanted to believe it could happen, but experience had not given him any reason to hope for it.

"Can we agree that I don't roll with the emotional punches the way you and Lydia seem to?" he asked wryly. "I'm still figuring all of this out."

Stiles smirked at him. "You seemed to be rolling right along with things pretty well the other day," he teased good-naturedly.

Derek shrugged. "That was sex. Sex is easy." The look on Stiles' face told him he that wasn't a good enough response. "You and I… Nothing changed in that three months. It was as simple as it ever was. Adding Lydia wasn't hard because she made herself impossible to resist."

"Now you know why I couldn't resist her," Stiles pointed out, and Derek went silent. Stiles cursed. "I'm sorry, Der. I didn't mean to remind you."

Derek shook his head. "It's part of our history," he said ruefully. "It's not a part I enjoy, but it happened."

"If it makes you feel any better, the decision wasn't as easy as I made it out to be," Stiles admitted quietly. "Part of me felt like there was no decision to make because I loved Lydia, I knew she loved me, and she was the one I'd always wanted to spend the rest of my life with. But I didn't want to leave you. I didn't want to leave us."

"You did, anyway." His face was stoic, hiding how much it still hurt to have been left.

Stiles rubbed a hand over his face. "I know. It didn't seem like you were a choice, not really. I mean, you didn't do the relationship thing, you know? You did sex. We had sex, a lot of it, and it was good. Scratch that, it was fucking fantastic. But I never had a clue that you actually felt anything for me beyond wanting to fuck me."

Derek was quiet, not sure how to approach that. It didn't erase the pain, but it wasn't like he didn't understand where Stiles' decision had come from. Lydia was a sure bet. Derek was a risk. He got that. On the flip side… "I don't know how you couldn't see that I was head-over-heels for you," he replied evenly. "You've known me long enough to know I don't use my words when I can use action instead. I would have thought you could read what I was doing instead of what I wasn't saying."

Stiles considered that. "Maybe I could," he admitted, voice low. "Maybe I was just afraid to be honest with myself because it meant I would have had to turn Lydia down in order to take a chance on us. And, if you know me at all, you know how inconceivable the idea of walking away from Lydia Martin would be."

Derek nodded. He knew Stiles all too well.

"I know I should have said something to you before giving up on us." The words were halting, aching. "I'm sorry I did that to you. To both of us. I caused us both so much pain. I never wanted to let you go, but I couldn't let her go, either."

"Well, you don't have to worry about that anymore," Derek commented dryly. "If Lydia has her way, you'll become the first guy ever to have a girlfriend and a boyfriend at the same time, with permission from both," he added with a smirk. Stiles just stared at him, and he mentally reviewed what he'd just said to figure out what had caused the reaction. Nothing came to mind. "What?"

"That's, uh, the first time you've ever said that," he mumbled, squirming in discomfort.

"Said what?" Derek asked, still not understanding. Stiles flushed, ducking his head.

"You called yourself my boyfriend."

Derek was struck speechless. He hadn't realized how casually he'd thrown out the term, and now that he had, he was surprised at how comfortable he was with it. Stiles was his boyfriend. The thought almost made a giddy smile creep onto his lips, but he willed it back and simply looked back at Stiles blandly. "I am. Aren't I?"

Stiles grinned hugely and threw himself at Derek, wrapping his arms around the wolf's neck and planting an enthusiastic kiss on his mouth. "You bet your fantastic ass you are."

The exuberant embrace made him laugh; he couldn't help it. He'd never been with someone so full of life and energy and pure happiness, and despite his best efforts, Stiles had rubbed off on him in a significant way. And in more than one, he thought to himself with a wry grin.

Derek sank back into the couch and Stiles followed him, leaning across his chest with his head tucked just underneath Derek's chin. His arm came up unthinkingly to wrap over Stiles' collar bone and they fell into a comfortable silence, until Stiles piped up with, "We've never really talked about how much money you have but I know it has to be a lot considering you own this whole building, so, I don't know, do you think maybe you could redecorate again? This stuff sucks."

He twisted his head to look up as Derek glanced down with a wounded pout. "I like my place."

Stiles snorted. "Of course you don't," he objected. "This stuff is all hard and bland and boring. I liked the last decorating scheme a lot better."

Derek glanced around, noting ruefully that Stiles was right. "Maybe the three of us should go shopping," he suggested lightly. "Considering this is home base for us now, we should all be happy with it."

Stiles popped up, gaping at him. "Did you just say what I think you said?"

Frowning, Derek cocked his head. "You keep reacting like I'm saying these stunning things, but I'm not."

"You said 'three of us', and 'all'. You're really into this now, aren't you?"

"What else am I supposed to be?" he asked, baffled. "I agreed to do this."

"But you're thinking long-term," Stiles clarified, leaning into him and pressing a kiss to his jaw. "You're not assuming it's going to fail."

He softened, shaking his head. "No, I'm not assuming it's going to fail," he conceded. Sighing, he slid an arm around Stiles' shoulders and pulled him in. "I love you." No matter how many times he said it, it would never be any less scary, he mused. Or less thrilling. "Lydia loves you. You love us. As weird and complicated as this is for me, those three facts make it simple. I owe it to both of us to try to make this work instead of sabotaging it."

"Thank you," Stiles murmured. "Thank you for trying, for all of us. I know getting to this point hasn't been easy, and it's not going to be much easier anytime soon. It's going to continuously take work. Even in ten years, it's still going to take work. But it'll be worth it."

"Jesus. Ten years? You really think the three of us will make it that far?" A soft huff of laughter blew warm breath against his chest, and Derek glanced down bemusedly. "Care to share?"

"I was just thinking of how far we've already come since the first time you kissed me," Stiles admitted, stroking his thumb over Derek's. "I was terrified you were going to kick my ass and then you were kissing me instead, and my brain was half screaming to run with it and half freaking out because there was no way you meant it."

"I surprised myself," he confessed. "It wasn't like I hadn't had the thoughts before, I just discarded them. I didn't think anything would ever come of them."

"A lot came of them," Stiles joked. "A lot of times."

Derek groaned. "You and your dirty mind." His eyes warmed as Stiles sat up and pulled him in for a lingering kiss.

"You wouldn't change me even if you could," Stiles teased after they broke apart, each taking a much-needed breath.

"No," Derek agreed fondly, sliding his fingers between Stiles' and tangling them together. "I wouldn't change a damn thing."