Alrighty, my first attempt at an Undertale lemon, and it's a yoai incest-in-law. Off to a great start people. As the summary said, this fic was inspired by a few Undertale fan comics. I'd love to give them credit, but I can't find them and don't really remember their names, so disclaimer: if you see something here from a comic or see a comic that had something from here, I do not own nor do I claim to own them. Now, on with the shameless smut! Also, for the purposes of this fic, Frisk will be male. You wouldn't think that I would have to point that out, but you'd be surprised.
It had been quite a long time since monsters had returned to the surface. It had been hard work, but with Frisk's help, they had been able to re-enter the surface world, and were now a part of society. There were bumps here and there, monsters being so different, even from each other, was unnerving to some humans, but for the most part, things were going great.
Frisk was currently nineteen years old. He and his technique brother in law Asriel had gotten a house together awhile back in a burst of independence and pride, though to be honest the house was just down the road from Toriel, as neither Frisk nor Asriel was quite ready to handle being too far away from their mother and vice versa; which would have earned them mocking if not for the...complex circumstances.
Regardless, things were looking up on all sides. It was currently Sunday, and neither Frisk nor Asriel had anything to do for the day. Toriel sent over a box of things from when they had been kids still living with her. She had kept quite a few things over the years, including a box containing various tapes that she'd taken of them.
"Wanna watch?" Frisk asked. Having no way of knowing what was about to happen because of his response, Asriel nodded, "Sure why not." He said, plucking a random tape from the box and going to the TV. There were three scenes recorded on the tape, the first being Frisk and Asriel at a school play which Toriel had found adorable, but they had found unimaginably boring both then and now. The second was of them at Christmas, opening various presents they had gotten that year.
The third though, was the cause for the commotion that followed it. It showed Asriel and Frisk, still very young, only a few months after they had left the Underground, playing happily in the front yard of the house. The topic of what they would do came up, and the two children both began reciting the extreme things they assumed they would do as grown ups; though ironically their extreme claims were quite mundane when compared to the adventures they had both been through.
"When we get older, I'm gonna marry Frisk!" Young Asriel shouted confidently, smiling proudly at the claim as he hugged his brother in law. The present day Asriel felt his face begin to burn red, all too aware of Frisk sitting only a few inches away, seeing the same tape he was. "We're gonna marry!" Young Asriel shouted again, Toriel giggling from behind the camera before the video ended with Frisk giving Asriel a kiss on the forehead.
The tape ended, and the room went dead silent. Asriel was hoping, praying that Frisk would just let it go without teasing him. No such luck. "So...do you still wanna-" Frisk started, Asriel interrupting him, "Oh shut up!" He said, flustered and embarrassed. This was not something he wanted to deal with.
The truth was, those words hadn't just been something stupid he had said as a kid. Over the years, he'd developed a crush on Frisk, though honestly it was reasonable to say he'd been in love with him before they had even left the Underground. Unwilling to let a rejection and heartbreak soil the 'happy ended', especially from Frisk of all people, Asriel decided to simply ignore the feelings whenever they rose up.
Needless to say, the strategy hadn't worked out so well, especially now.
Frisk narrowed his eyes at Asriel, "I think you misunderstood me." He said, reaching down, grabbing Asriel around the chest, and pulling him up onto the bed. "W-what do you mean?" Asriel questioned.
Frisk chuckled, "Do you remember when I got you to the surface?" Frisk asked. Asriel nodded, unable to help smiling at the memory.
"Frisk, don't you have anything better to do?" Asriel asked, only for an impatient young Frisk to pick him up and take off running, "You're coming with me you little cutie!"
Frisk had known nothing he said would have convinced Asriel to go back with him, so he had made him. And shockingly, he had never reverted back to Flowey, even though he was certain he should've. He was never sure why, but he liked to think that it was Frisk's determination that kept him going. It was this incident that had initially triggered Asriel's feeling for Frisk.
"I wasn't about to let you waste your life, even if you only had a little life left." Frisk said, "I reset so many times, doing the same thing over and over, just because I wanted to save you." "How..how many times?" Asriel had never asked, as he felt it wasn't his place to.
Frisk gave a small smile, "Three hundred and sixteen. I made small changes here and there, but I kept my pacifism the whole way through. I knew I could've ended up doing something bad if I kept resetting, I could've given in and gone back, but every time I reset, I did so because I wanted to save you to. If I didn't, it wouldn't be right."
"I know..Asriel said, "I was all that was left for the 'happy ending'."
Frisk glared at this, "Don't say that. I wasn't saving you for my happy ending. I needed you to have yours. You deserved it, far more than I ever did."
Asriel was shocked by this. He hadn't thought there was anyone who deserved happiness more than Frisk, especially not himself. "And do you know why I spent all that time trying to save you?" Frisk asked.
Asriel shook his head, not having any idea. Frisk pulled Asriel to him so his back was pressed to Frisk's chest. "Because I love you Asriel." He said softly, "So let me ask you again, and no interrupting this time," Frisk added, "Do you still wanna get married~?"
Asriel was shocked to say the least. Obviously words would not suffice as any kind of answer for this, so Asriel, after a small pause to work up the nerve, allowed everything hope, every 'what if', ever desire he had had over the passed few years to bubble up into an action. He turned, grabbing Frisk's shoulders and pulling him into a kiss.
Honestly, Frisk didn't seem shocked by it, more like he was relieved, as though he had been terrified that Asriel wouldn't start making out with him, and he would have to pretend he had been just joking around. But luckily Asriel had reached his limit of pretending he didn't want it, and Frisk had never been one for postponing romance. He often flirted without even knowing it after all.
Frisk kissed Asriel back, his hands working under his shirt to feel along Asriel's body. From the intimate way they moved, as though trying to memorize ever detail, Asriel realized that Frisk must have been wanting this for a long time, possibly as long as Asriel himself had been wanting it. Asriel kicked himself for not taking the leap sooner.
Frisk reluctantly broke the kiss, but did so only so Asriel could remove his shirt. Frisk did the same, and then the two continued their kiss, Frisk's tongue invading Asriel's mouth. He may have been on bottom, but Frisk was very clearly in charge of this. He tugged at Asriel's pants, and the goat boy nervously began pulling them down as they continued to make out.
Bit by bit they both lost their clothes until they were laying naked together on the bed. Asriel was blushing madly from Frisk being able to not only see him naked, but able to see how hard he was. He was only about six inches in length. It was about an average size for humans, but small for a boss monster. He felt even smaller when in comparison to Frisk's solid eight and a half inches.
All his anxieties on the matter vanished however when his mind snapped back to the present and he realized that Frisk was blushing just as hard as he was, and from how he was shifting around, just as worried about what Asriel would think of him naked.
Unwilling to let Frisk think for even a second that anything about him could disappoint him, Asriel leaned down and gripped Frisk's shaft. Frisk moaned just from the touch, Asriel's grip being soft and warm thanks to his fur. Asriel began moving his hand slowly, mimicking the motions he knew full well from 'practice' on himself.
Frisk's soft moans only picked up as Asriel went on. Seeing how much Frisk was enjoying his touch only helped Asriel get braver, and soon he leaned his head down to lick at the pre-cum that had started to leak from Frisk's tip. Frisk groaned, "O-oh god Asriel~"
Frisk placed his hand on Asriel's head, which spurred Asriel to push his head down and take Frisk's head in his mouth. Frisk gasped, moaning loudly. Asriel pushed his head down, taking more of his length.
Frisk groaned at how warm and wet his mouth felt around his rod. He couldn't help thrusting up into his mouth for more. Asriel forced himself not to gag, taking Frisk halfway down as he begun sucking on his cock. Frisk grunted and groaned, holding Asriel's head where it was, "A-Asriel, I'm gonna c-cum!" Frisk moaned.
Asriel bobbed his head faster, wanting, needing, to make Frisk cum. Frisk yelped in pleasure as he came, firing several strands of hot cum into Asriel's mouth. Asriel swallowed instinctively, finding that Frisk's cum actually tasted very good. Asriel looked up for approval, seeing Frisk panting with a smile, "That..was..great." He said.
Asriel smiled proudly, "Now how about I hate I return the favor~?" Frisk purred with a grin. Asriel blushed deeply, "W-well.." He said, shifting onto his fours. Frisk grinned, "Right to it huh~?"
"I c-can't wait frisk," Asriel said, squirming, "I promise I'll think of something even better for the wedding night~"
Frisk grinned wider, lining his member up to Asriel's rump. He couldn't help giving it a squeeze first, loving how soft it felt. Asriel moaned softly at the squeeze, then moaned louder when Frisk started to thrust inside him. Frisk pushed in slowly, Asriel moaning louder as he got deeper. Asriel had never taken anything inside his ass before, save for his own fingers on occasion, and the feeling was so intense he gripped the bed, moaning loudly.
"F-Frisk!" Asriel moaned, beginning to move his hips against Frisk's. Frisk grunted, holding Asriel's hips as he pushed his cock deeper into Asriel's tight puckered hole. "You feel so good~" Frisk moaned, beginning to pick up the speed.
Soon the bed began to shake from the combined force of their movements. Asriel could feel Frisk's balls slap against him as Frisk rammed balls deep into him. Asriel tensed up, getting tighter around Frisk as he came, "Frisk!" He shouted in pleasure, his arms giving out. Frisk kept thrusting into him for a few more moments before cumming hard inside him.
Frisk laid on top of Asriel, holding the monster boy close as they both panted hard. They laid together for several minutes before Asriel shifted over so they could start making out again.
"Now Asriel said when they finally broke the kiss, "About a ring..."
And that's a wrap! Sorry if it seems rushed at all, like I said it was my first Undertale fic, not to mention my first full yaoi fic. Consider this the jumping off point for better things to come. Until next time, I am sinful by nature with no malicious intent, and I'll see you all next time!