Here's some car sex in the middle of a serious Arc, and that image up there is what Rin is wearing. On another note, I've had to vastly modify the Blue Night Investigation Arc to get the results I want for this story, as well as go more in-depth on theories I've come up with for this fandom. I hope you're enjoying this story so far! Happy reading!

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Mephisto suggested they all go their separate way to take a break after what had just happened and all the I formation they'd just taken in. Lightning said he'd like to go through the files with Rin later after dinner that day. Before he could escape to his apartment to change his clothes, Mephisto had Belial and a couple other servants grab the man to force him into a bath in the Manor. He was covered in nasty fluids from the clones. Bon was also covered, but Amaimon would gladly wash the boy off in a bath all to themselves(the Manor had 12 bathrooms, there were plenty to use).

Mephisto held Rin against him and shut the door. He started off with kisses to Rin's neck and jaw–just gentle pecks. Rin relaxed against him and sighed. He let the man do as he wished for a moment. His tail unfurled from around his waist and swayed in the air, showing his enjoyment of his lover's ministrations.

"Taking this limo.was a good idea, Lovely. There's much more room in this one than the pink one." Mephisto purred against Rin's neck. Rin purred in response, catching the Time Lord's lips in a hungry kiss. Rin's tongue piercing clinked against their teeth.

Mephisto pulled Rin up to straddle his lap, thighs on either side of the man's hips. Rin tangled a hand in the Demon King's hair, tilting his head to the side to give the man more room on his neck. Mephisto nipped at the spot Rin's pheromones poured from and it snet a jolt through the half-demon's body. That spot was incredibly sensitive. The limo was filled with their scents combined as they got more and more worked up.

Rin grinded down into Mephisto's lap and the man groaned. He grabbed Rin's hips and thrust up as he pulled the boy down against him. The feeling was electric and Rin shuddered. Mephisto was enjoying feeling up Rin's ass under the black skirt he'd chosen to wear that day. Rin looked so much better in tailor fitted clothes compared to his old donated clothes from the monastery. Mephisto had enjoyed watching them burn.

He squeezed Rin's ass in his hands and enjoyed the moan he got from the half-demon for it. Rin's outfit was beautiful and looked perfect on him, but Mephisto didn't feel like undressing them both the normal way, so he snapped their clothes into folded piles on the other side of the limo. The friction of skin on skin between them felt even better and Mephisto thumbed the base of Rin's tail with one hand, the other dipping between his cheeks to just barely brush the entrance there.

He took his time examining Rin's body. Rin was still slim, but he'd packed on some muscle from training lately. He was short and only weighed 63 kg, but his body was solid. There was just the right ratio of muscle to fat. Mephisto loved grabbing him at any opportunity, loved feeling the solid muscle where it looked like soft flesh. He knew Amaimon and Bon liked doing that too and Rin and by now gotten used to it.

Rin cried out in surprise and bucked this hips at the touch to his tail and the barest touch to his entrance. "You used to despise having a tail, now look how far you've come, Dearest." Mephisto chuckled, stroking his claws against the grain of the fur and getting another precious noise out of his lover. Just to see the teen's reaction, Mephisto gave a harsh slap to Rin's bare ass. He got a yelp for it, but no sounds of pain. In fact, the blush on Rin's face turned an even darker shade of red and Mephisto grinned.

Oh?

He takes his claws down Rin's thigh–not hard enough to break skin, but hard enough to at least sting. Rin squirmed, letting out a weka moan. He hid his burning face in the crook of Mephisto's neck as the man laughed. "Well this is an interesting development...." He purred in Rin's ear. He snapped again and a bottle of lube(cherry scented because he was a fancy bastard)squeezed some onto his fingers.

He reached down and plunged one finger in to the first knuckle. Rin tensed up, but only shifted his hips at the sensation. Mephisto grinned and pulled the finger out, then rammed two all the way in. Rin shouted, arching against the Time Lord. Rin rutted forward so his dick slid against Mephisto's and back so Mephisto's fingers would go deeper. The Demon King let him fuck himself on his fingers for a shirt while, enjoying the shameless effort Rin put into it to get himself off.

He pulled his fingers out and rammed three in next. He crooked his fingers and hit the swollen gland he knew was there. Rin's head dropped to his lover's shoulder as he moaned, body shuddering. "Nnn, Please more, it feels so good Mephi~!" He breathed in the Demon's ear, tugging on the love with a fang.

Mephisto did as he was asked and kept ramming his fingers into Rin's prostate, not giving him even a moment to catch his breath. He hit that spot over and over again and Rin  was rocking back onto the fingers. His tail came around to wrap around both their dicks and stroke them. Rin's stroked got sloppy fast the closer he got to cumming. Mephisto was assaulting his prostate just like he'd asked, just like he loved and he was enjoying it immensly. "Are you close, Dearest?" Mephisto murmured to him breathlessly.

"Fuck–Gonna–Ah~! Gonna cum~!" Rin responded, hips working to get himself off. Mephisto could honestly cum just watching Rin come undone.  "Ngh~Shit!" Mephisto groaned as he spilled over both their dicks and Rin's tail. Rin's whole body trembled and he moaned Mephisto's name to the empty car as he came a second later.

Mephisto kept running over Rin's prostste just to see his reaction and to his surprise, Rin was enjoying it. He but his lip at the overstimulation, whimpering, but his hips still rocked back onto the fingers.

"Ngh~Please, keep going~!" He pleaded. Mephisto smirked and pulled his fingers out. Rin whined, but it turned into a moan when the Time Lord grabbed the bottle of lube, pushed the top of it inside Rin, and squirted it. Rin jolted forward in surprise at the cold liquid shooting into him. Before he could ask what Mephisto was doing, the Demon's tail slid into him. The feather-like end had folded together and went in easy. Mephisto's tail got bigger from the tip though and he watched Rin's reaction carefully.

Rin looked surprised, but turned on at the same time. He gave a loud moan when Mephisto pulled it out some and then thrust back in harshly. Mephisto set a harsh pace from then on, fucking his tail up into Rin roughly and hitting his prostate every time. Rin let lose cried only he and Mephisto could hear in the limo, holding onto the man for dear life as he was fucked raw by the thick tail.

"God, please don't stop–fuck~!" Rin arched, against Mephisto, holding onto him with his claws as he came a second time, still rocking his hips. "Nngh–yes, fuck, please don't stop–Ah~!" He begged, hips stuttering as he came, but not stopping their frantic movement. Mephisto was almost to his limit, but he pressed on, keeping the rough pace until the end.

His tail stopped pistoning into Rin and instead pushed in with deep grinds. Rin whined, but the Demon King didn't let up the slower pace. He knew it was driving Rin crazy how slow he was going now. He wanted to see Rin cry. He loved watching the boy beg for him to go faster, go harder, to 'please God, just make him cum!'

Rin buried his face in Mephisto's neck. He growled deep in his chest and bit down, fangs sinking all the way into the muscle and locking in. It almost felt like he wanted to bite off that chunk of flesh from Mephisto's shoulder and he groaned and the mix of pain and pleasure. He held Rin's hips still on retaliation and Rin whined into his shoulder. The tail was moving so slow and he wanted to cum so bad and God, why was he sleeping with such a sadistic asshole?

He whined, trying to move his hips. A minute later, he pulled out his Trump vard–distress pheromones. Mephisto couldn't fight the urge to make Rin feel better when the distress pheromones made it to his senses. Rin knew this and whenever he didn't wanna beg, he'd do this instead.

Mephisto groaned and his grip loosened on Rin's hips and Rin was able to Rick back into the thrusts, purring against the flesh in his mouth. He didn't know why, but he just didn't wanna let go of Mephisto's shoulder. He wanted to sorry grooves into it with his fangs and stay there until he came.

Finally, Mephisto pulled his tail nearly all the way out and rammed straight into Rin's prostate, giving the base of Rin's tail a light tug at the same time. Rin whimpered out his release into Mephisto's shoulder, letting his hips come to a stop in their fucking as he felt Mephisto cum between them too.

Rin unlatched from Mephisto's shoulder and licked over it lovingly, kissing the bite mark over and over again, like they'd make it stay even though he knew it would heal in a day or two. Mephisto purred and pulled his tail out of the boy. Rin purred in response and they sat there for a minute, completely relaxed.

"I suppose we should get ready for dinner." The Time Lord sighed. Rin gave a complaining noise and kept peppering slow kisses onto the man's jaw. He didn't want to move.

"Come now, there's still work to be done and conversations to be had. And tonight you get to stay up and go over data with Lightning. It'll be like a sleepover! Now let's go, Lovely." Mephisto reasoned. "Mnnn, fine...." Rin muttered, still kissing Mephisto's jaw. He sucked a mark into a spot behind Mephisto's ear and the demon chuckled.

"Aren't we cuddly today?" Rin grabbed his hand before he snapped them clean. "Wait."

He brought his tail up to his mouth and licked their mixed cum off of it. He gave a weak moan and shivered, but kept going until it was all clean. "Ah, fine, one more time." Mephisto Gabe in when he saw the boy's body trembling in response to the attention to his tail. He reached around and stroked the base of the tail with one hand, fingering Rin with three fingers with the other.

Rin's hips rocked into his ministrations until he came cane with a weak moan, body shuddering. "Fuck it feels so good~" He breathed into Mephisto's neck when he finished. "Sorry, it just felt too good." He apologized with a smile. "Oh don't apologize, I quite enjoy watching you come undone every time we do this." Mephisto pulled him into a slow kiss and Rin sighed contentedly.

"Now we go." He giggled. Mephisto snapped his fingers to clean them and dress them and they left the limo, locking it behind them.