As far as Adrien was concerned, what had happened between the two of them was a happy accident. To Nathaniel, it was a mortifying mistake.
Adrien had revealed his superhero identity to his boyfriend the day before their year anniversary, so Nathaniel was more than used to Chat Noir showing up at his window, begging with his giant kitten eyes to be let in.
Most of the time however, he sent a quick text warning Nathaniel that he was on his way so the redhead could clean up whatever he was working on without worrying about his mildly clumsy boyfriend ruining a painting. That was a mistake that only needed to be made once.
Of course, since it was the night before Nathaniel's birthday, Adrien decided to superhero up and head over, intent on lavishing his boyfriend in the absolute best birthday cuddles. With how excited he was, he hadn't even realized that he had forgotten to text until he got to the house and saw the window was shut.
With a smirk, Adrien decided that since Nathaniel was obviously unaware of his arrival, the best plan of action was obviouslyto sneak in and startle the boy. The thought made him chuckle, especially when he imagined the no doubt hilarious reaction that would come with it.
Nodding at himself, he lowered himself to all fours, creeping across the rooftop to the window, lifting his head just enough for him to peek into the window, pausing at the sound of the music playing. He didn't recognize the song, but he did recognize the soft voice that seemed to be singing along.
Using one of his claws to lift the clasp, he slid into the window silently, noticing that Nathaniel was sitting with his back to him, singing under his breath as he worked on whatever was in front of him. Straightening, he silently crept forward, grinning to himself before slamming his hands on the boy's shoulders, making sure not to use too much force.
The scream that he got in response made him wince, hands reaching up to clap over his ears, wincing at the ice cold glare his boyfriend sent him when he turned in his chair.
"What is wrong with you?" Nathaniel hissed, crossing his arms over his chest as Adrien sheepishly avoided his gaze, "You're lucky my family is out of town. I really don't feel like explaining why Chat Noir is sneaking in my window and scaring the shit out of me to anyone."
"Sorry," Adrien responded, dropping his transformation, "I wanted to give you birthday cuddles, but I guess I forgot to text to say I was coming over."
Nathaniel rolled his eyes, reaching behind himself to shut off the music that was coming from his laptop.
"What were you working on?" Adrien asked, raising an eyebrow when Nathaniel hurriedly reached back to shut his laptop, cheeks flushing red as he averted his eyes.
"Just homework. Forgot to do it yesterday and I couldn't sleep, so I was going to do it now."
Adrien smirked, leaning over Nathaniel and threading his fingers through the boy's bright hair.
"Really? I don't recall any teachers giving out homework this week, and the last homework we had, we turned in together," Adrien grinned, noticing how Nathaniel's ears seemed to pink slightly. "Also, I heard you singing~!"
Nathaniel looked mortified for a moment before he pulled his arms away from his chest and instead used his hands to cover his face with a groan.
"I didn't recognize the song, but your voice was incredible! Why didn't you tell me you could sing?" Adrien asked, grabbing the redhead and shifting them so he could sit on the chair while Nathaniel sat in his lap.
"Because I can't," Nathaniel whined, moving his hands, but shifting so he could bury his face in Adrien's neck. "It's just...the song reminded me of you and I was working on your present."
Adrien blinked a few times, flicking through important dates in his head as he tried to find one that would explain why Nathaniel was making a present for him.
"What was the present for?" He asked, hands raising from Nathaniel's waist to comb through the red locks.
Nathaniel shifted just enough that Adrien could see one sea blue eye and the corner of his nose before responding.
"It's my birthday."
Adrien raised an eyebrow in response, still confused.
"Yeah, your birthday. Why would you make a present for me?"
"I dunno, I guess it's silly. I just got the idea in my head and I wanted to share the day with you, especially since my family is going to be gone this weekend."
Adrien shook his head with a smile as he let his head fall back against the headrest of the chair.
"You didn't have to make me a gift. It's your birthday, not mine."
Nathaniel hummed in response, and when Adrien looked down, he noticed how tired the redhead really looked.
"Hey, Nath?" He asked, getting a hum in response, "Could you sing me what you were singing when I showed up?"
Nathaniel cracked one eye open, peering up at Adrien suspiciously before relaxing with a sigh.
"Fine, but you have to carry me to bed."
Adrien grinned, scooping his boyfriend up and carrying him over to the mattress on the other side of the room. Luckily, they were both in pajamas, so Adrien slid into the bed, laying back as Nathaniel cuddled up to him with a smile.
"Now, will you sing it for me? I'm tired, but I want to fall asleep to your voice."
Nathaniel hummed again, shifting for a moment before opening his mouth and singing for Adrien.
"Sometimes I just need a break, a little sunshine on a rainy day. My whole world changes with you. It's in the way you look at me, no words could say what your eyes speak…" Nathaniel trailed off, falling asleep against Adrien's chest.
And as Adrien fell asleep beside him, his only thought was that Nathaniel's singing was definitely the most beautiful thing he had ever heard, and now that he had it, he planned on having the redhead sing for him more often if possible.