Summary: Tao's eyebrows shot up, his mouth gaping. It was M-21 –there was no-one else it could be- but Tao had never seen him like that before.

Contains Tao/M-21, implied sex while in a mind altered state (werewolf instinct!M-21)

Post season 5.

Written for Key's birthday (and posted a day late, haaaahahah)

This fic is based around a Tao/M-21 verse that Key and I have been rping together for a while, but it should still make sense. The biggest reference I can think of is that in this particular verse, M-21 sometimes goes instinctual and horny if he practices his transformation a bit too much.

Full Moon

By Dark Ice Dragon

"Mm," Tao said, twirling the bottlecap between his fingers (he'd made sure there was no juice in there beforehand, so he wouldn't be splashing it all over Boss' kitchen floor). "It shouldn't take me too long to… Boss?" Boss had been nodding along to what he'd been saying, but his eyes had suddenly flicked to something over Tao's shoulder, his eyebrows drawing in, the corners of his mouth turning down.

Curious at what had gotten Boss' attention, Tao glanced over his shoulder and-

Oh.

Oh, shit.

His own eyebrows shot up, his mouth gaping. It was M-21 –there was no-one else it could be- but Tao had never seen him like that before.

'That' was transformed, but even when M-21 had transformed fully, he'd still had his human head. What was on top of M-21's shoulders was completely covered in fur, had a snout (with a pink scar just visible over his lip), and there were two triangular ears sitting on the top of his head going between erect and plastered against his skull. The fur around M-21's neck was practically a mane, spilling over his collar.

M-21's shirt was miraculously still on, though his buttons were straining against his now bigger chest, silver fur peeking through some of the gaps. Claw-tipped hands covered in fur were standard - below that though, M-21 wasn't wearing trousers. There were a few small trails of blood over his legs, and Tao could understand why – M-21's legs had rearranged themselves so they were like a wolf's, even his feet turned into wide paws. Trousers didn't have enough space to accommodate that.

And then there was the tail, flicking left and right in a nervous beat.

"M…" Tao whispered. They'd finally narrowed down what had been making M-21 lose his senses, but it usually took him a while to start transforming, especially this much.

M-21 perked up at the sound of his voice, his ears swivelling towards him. M-21 ambled over, and Tao left Boss' side to meet him, studying his walk – he was unhurried but direct; Tao wasn't sure if that was normal, since M-21 seemed to always lose his senses the nights he was distracted with work, coming up behind him. Then again, he was usually busy with work…

Tao had expected his lips being licked as soon as they were close enough, M-21's tongue wider and rougher than before. It was hotter too. M-21 was mindful of his claws on Tao's shoulders, and Tao pulled back to study him, curious at the change in his normal behaviour. Usually, M-21's first course of action was trying to rip his clothes off.

M-21 didn't try to close the distance, calmly blinking at him. Huh. So that transformation wasn't the only thing different this time.

"M…?" Maybe M-21 was still able to think and he'd only transformed?

He got a low rumble in response, throaty and sounding far closer to a growl than Tao had heard him make. M-21 nuzzled around his mouth, but that was it.

Chuckling softly, Tao murmured, "Yes, it's good to see you too." He buried his hands into the fur at M-21's neck, and was surprised at how soft it was under his fingers. "You've got natural conditioner, huh?"

Another rumble, and it didn't seem like M-21 was trying to occupy the space Tao was in. Still. He tilted his head away from M-21's face. "Boss?" Would it be better to do some tests now or go up to their bedroom in case M-21 tried to jump him while they were in the middle of them?

"If you can lead him downstairs, I'll have a few tests prepared."

"Got it." Tao heard him leave the living room, the door closing behind him. "Come on," Tao said to M-21, "Boss is going to put you through the scanner."

Another grumble, a half-sigh in there, and M-21 stepped away.

Tao glanced out the window and smothered a laugh when he saw the full moon shining through it. Oh, of course. "It's the full moon, you're fully transformed, you're instinctual, but you're not horny." He shook his head. "Only you would do that." Even if it hadn't been intentional.

M-21 cocked his head at him, making a questioning sound.

"Never mind," Tao said, smiling at him. "Let's go." He'd tease him about it when M-21 could react properly.

M-21 nodded, following him downstairs.

xOx

After the scans, Tao led M-21 back up the stairs going to their bedroom. The scans had only taken a few minutes but Tao could see M-21's ears were flicking back and forth, starting to lean towards staying flat, and he was shaking a little.

"Are you tired, M?" Tao murmured, opening the door. M-21's transformation limit was usually just over ten minutes, and that was with his regular transformation; with this one, Tao wasn't surprised he was already there.

M-21 nodded, a low groan at the back of his throat.

"Come on, then," Tao said, "bed." He went in first, then lifted the covers for M-21, who pressed in close once he was in. M-21 was trembling harder, his ears flat against his skull.

"M," Tao said softly, "you have to let go of the transformation." Even if M-21 was going to be instinctual for the rest of the night, there was no way he would be able to stay transformed for that long.

M-21 didn't respond, his eyes squeezed shut. Damn.

"M," Tao repeated, putting more force behind his words.

M-21's trembling eased a little bit, and his eyes fluttered open, his ears pricked towards him. "Nng…?"

He made sure he had eye contact and said firmly, "Let go of the transformation."

"Nng." M-21 gave him a weak nod and did as he was told. The fur was the first to go, rippling before looking like it was being sucked back into his skin. At the same time, M-21's snout shrank, his wolf ears moving down his skull, becoming rounder again.

M-21's expression was still open, his eyes wider than usual, but that was too much to hope he would regain his senses that easily.

"Feel better?" Tao asked him, lifting an arm to start threading his fingers through M-21's hair.

M-21's eyes half-lidded at the contact, pushing against his fingers slightly, like Tao knew he would. "Mm…"

"Good." M-21 eventually settled down, sighing as he closed his eyes. "Thaaat's right, just go to sleep – you need it after that."

M-21 made another soft grumbling sound, his breathing deepening.

Tao smiled, continuing to run his fingers through his hair. After a minute, M-21 was asleep.

Well, it was late, and he didn't have a lot to do so Tao made himself comfortable and joined M-21.

xOx

M-21 woke up slowly, feeling Tao's warm body next to him.

…Wait. M-21 moved his legs, double-checking what he was feeling - he wasn't wearing trousers. And he didn't remember going to bed. Fuck. Again? But he hadn't been practicing his transformation yesterday. What had happened now?

He sighed, covering his face with a hand. But… M-21 blinked, lifting his arm to inspect it – he was still wearing a shirt. And when he looked at Tao, he could see Tao was fully clothed. Something wasn't adding up.

M-21 sniffed the air discreetly but didn't smell sex, or even arousal. Huh.

Tao shifted, murmuring under his breath before his eyes fluttered open. When Tao saw he was awake, he smiled. "Morning."

"What happened last night?"

Tao snickered, which made M-21 relax a bit – whatever it was, it couldn't have been that serious, then. "You transformed – fully." What…? "I mean, like-" Tao started waving his hands in front of his own face, like he was holding a big ball in front of it. "-you had a snout, your entire face was covered in fur, and your ears had moved to the top of your head!" His hands were above his head now, mimicking dog ears.

"What," M-21 said flatly. Tao had to be joking – his transformation had never gone that far before, but Tao wouldn't joke about that either.

"I'm being serious!" Tao glanced elsewhere in thought for a second. "Hold on." Tao got out of bed, patting his shoulder as he did, and brought back his laptop. Leaning back against the headboard, Tao tapped something out and then turned it around so M-21 could see the screen. "See?"

Right there in the centre of the screen was Tao and a werewolf, walking down the corridor outside the living room. A silver werewolf, wearing a white shirt, and M-21 could just see the scar going along the right side of the lip.

"Fuck," M-21 said, slumping. Not only did he have to worry about losing his senses, he had to worry about his entire body changing as well? Was he going to end up with a massive wolf form too?

Tao patted his shoulder again. "It's fine – Boss did a couple tests so if there's anything new, we'll know."

"'If' there's anything new," M-21 repeated flatly. "That was pretty fucking new."

"It… Heh." Tao chuckled, a small smile on his face. "It was a full moon last night."

M-21 grimaced. That… Ugh. "Of course." That would make sense, wouldn't it?

"Yeah." Tao nodded. "You fully transformed, went instinctual but you didn't get horny, so you were breaking expectations as usual, heh."

Tao's expression softened, looking down at him. "You all right?"

"Yeah," M-21 breathed out, closing his eyes. "Just another thing I have to get used to."

He stilled when warm lips were pressed to his. Slowly, he relaxed, returning the kiss, feeling Tao rest his hand on his shoulder.

"In the very least," Tao said when he pulled away, "it'll probably only be once a month, and by then, we might have figured something out."

"Mm…" He just hoped in the meantime, something else didn't crop up.