The next phase of the experiment was underway.

Fenrir, still on his back and tied to the bed, now found it significantly harder to breath. Why? Well, because he had Serra sitting on his face. Despite how petite her body was, her wide hips and thighs guaranteed that she had plenty to cover his head with. Fortunately, though, he was actually allowed to do something… so long as that something was eating out his girlfriend. In fact, that was the only way he would be allowed to easily breathe again.

He had to make Serra cum.

Serra made sure to sit down on his head facing the top of it. That allowed her to still look down at his eyes every now and then. Each time she looked at him, he would see her watching her with that smug, lewd smile of hers and eyes full of lust as slipped his tongue around inside of her passage.

Seeing her look down at him as he pleasured her… well, it was nice. Incredibly nice. Fenrir might not have been a particularly masochist nor submissive man, but such a situation excelled in amplifying that side of him. He wanted nothing more than to please his girlfriend and make her cum as hard as he could with what limited actions he was allowed to perform.

And on top of that was the ultimate reward in exchange for his obedient service. If he didn’t already feel submissive, then he did once he felt Serra run her fingers through his hair to pet his head between his ears. And then… “Good boy,” Serra whispered just a second prior to biting her lower lip.

Fenrir’s length wasn’t even being worked and he felt like he was on the verge of cumming from hearing that. Instead of shooting out his seed, all he did was let out a muffled moan of pleasure against Serra.

“Woah, that was effective,” Eva said. She hadn’t mounted Fenrir yet, but she was positioned just in front of his throbbing cock begging for some stimulation. “I wonder if it would be possible to make the test subject ejaculate simply from praising him.”

Serra was tempted to try. “Heh. He’s a praise slut. Like a little puppy.”

“Now he’s throbbing even more. I had no idea the subject was into such play and being told things like that.”

“He’s into a lot. And he doesn’t judge, so you can say almost anything you want to him. As long as you’re enjoying yourself, he’ll enjoy himself. Unless it’s one of Nell’s big fantasies.”

“Hard to blame him for that one considering what her fantasies are like.”

Serra shrugged her shoulders just a tiny bit before grinding her crotch down against Fenrir’s face even harder than before, forcing his tongue as deep into her passage as she could get it.

As for Eva, it was finally time to mount Fenrir. Finally for her, of course. She couldn’t wait any longer. The more she watched his aching length throb and leak precum, the more she wanted to feel its every movement within her. Not to mention that watching Serra ride his face was arousing her just as much. Cassiel might have been the most attractive in the eyes of Eva, but it was hard for anybody to top Serra when it came to actual actions. It was as if Serra always knew exactly what to do in any lewd situation to make it exponentially more arousing and fun for everybody involved.

“Who’s a good boy?” Serra asked Fenrir.

Fenrir tried to tilt his head back to push his tongue up even farther into her in an attempt to answer her that he was, in fact, the good boy. At the same time, he made Eva jump and giggle.

When Serra turned her head to look back at Eva and see what that was about, she noticed Fenrir’s tail wagging between his legs.

“His tail tickled my thighs,” Eva explained.

“Ooh, that gives me an idea,” Serra said. “I want to try using his tail to tickle somebody. Like tying down Cass Cass and then using his tail to tickle her. Or Aza. Tickling Aza would make her jiggle all over.”

“Why not both? We could perform an experiment to see who is the most ticklish when exposed to the test subject’s tail.”

“Good point. Oh, I just thought of a fun way to tease him.”

“What?”

“One of you could put his tail between your boobs. It would be like a titfuck, but with his tail just to tease him. And I think it would be fun to try and keep it between them while it’s trying to wag.”

“You have a point. I am sure the test subject would feel a combination of emotions seeing one of his girlfriends wrap her breasts around his tail rather than his reproductive organ while he is forced to watch.”

“Exactly. Happy but jealous of his own tail. Oh, I thought of another experiment.”

“What?”

“Blindfolding him and then making him try to guess who is doing what to him. Like have everybody give him a blowjob, and he has to guess which mouth is which. Same with handjobs. And titfucks. And riding.”

“You’re good at coming up with experiments. It would be interesting to see how many guesses the test subject is able to get correct. It would be a true test of his knowledge regarding our bodies.”

Serra nodded before letting out a soft moan due to the working of Fenrir’s tongue. “I think—I think he likes our plans.”

“I am not surprised in the slightest,” Eva answered. Thanks to still not actually riding him yet, she was able to keep up her scientist roleplay a bit more easily. But, at that point, she really couldn’t hold back any longer nor did she have any intention to. That was why she finally scooted a bit farther up on his thighs to position herself directly over his throbbing length. Next came a single hand that delicately wrapped its fingers around the base of his shaft. Once she had his cock held still, she slowly lowered herself down onto it until she could feel its tip glistening with his precum press up between her lower lips. It took no time at all for the precum around his shaft to become replaced with Eva’s own arousal. Now, with her head rolled back in blissful relief over finally having him inside of her, she let out a moan and said, “The—the subject’s… reproductive organ, is capable of providing—fuck.”

Serra couldn’t help but to snerk when she heard that. “Capable of providing fuck. I’m stealing that.”

“I… I don’t care about the play anymore, I just need this.”

“Then ride him. Less talking, more riding.”

“Good—good idea.”

Fenrir was starting to struggle. It had been so long between Serra’s thighs without a good chance to take a full breath that he was struggling to breathe but, when he felt Eva finally slide onto his cock, he found the strength to continue on. His dick was finally getting what it was so eagerly waiting for, so it was his turn to give Serra what she was waiting for and to make her cum.

Though, it was hard for him to actually do much considering how firmly she was rubbing herself down against his face. He didn’t even have enough mobility to move and give her clit any attention. All he could do was thrust and swirl his tongue around inside of her to the best of his ability. Technically, he could have been rubbing his nose against her clit… but he figured that would be ridiculous and just make them both laugh instead. So, he avoided purposely trying to pleasure her clit using his nose. It still rubbed against her clit every now and then, but there was no purposeful nose grinding.

“I waited—too long, for this,” Eva said, now steadily rising and dropping her hips onto Fenrir.

As for Serra, she decided to increase the fun for both her and Eva by turning around on Fenrir’s head, giving him a quick chance to breathe, so that she was facing the other women instead. That allowed her to wrap her arms around Eva’s waist to pull her a bit closer. And that allowed Serra to press her lips up against Eva’s, prompting the beginning of a make out session between the two women as one rode Fenrir’s cock while the other rode his face.

Between the two women on top of him and the fact that he was tied down to the bed still, Fenrir couldn’t move too much, but he did at least try thrusting up into Eva every now and then. Considering that she didn’t punish him or stop what they were doing, he figured he was allowed to continue. Though, at that point, he was pretty sure that Eva just didn’t care and wanted to cum.

That was why he tried his best to help them both cum at the same time… while also helping himself, of course. After all the teasing he had to go through, he desperately wanted to cum. There may have never been a moment where he wanted to cum more than he did while tied down to the bed. Even Serra never denied him from an orgasm for so long before.

It was a miracle he even managed to remain submissive for so long.

Now that he was actually inside of Eva, he couldn’t hold back. Even those subtle thrusts of his became blatant bucking his hips upward to fuck her as best he could. He needed to cum and wasn’t going to wait any longer.

And as soon as he heard Eva cum, he knew he didn’t have to hold back. He could cum without feeling any guilt about finishing before her.

“Fu-fuck,” Eva moaned out, not even able to continue making out with Serra. She had to wrap her arms around Serra’s smaller figure just to steady herself so that she didn’t fall off of Fenrir. Meanwhile, Fenrir kept thrusting up into her even as her own movements slowed to a halt.

It didn’t take long after that for Eva to feel Fenrir’s seed flood into her. His entire body spasmed, reminding the girls of a chained beast trying to break free, as his grunted out against Serra’s pussy.

At that point, he had no idea if he ever even made Serra cum. He was pretty sure that he didn’t since she seemed more or less calm that entire time. That was why he was surprised when she got off of his face to lie down by his side instead.

Without Serra there to help Eva stay upward, Eva flopped down and landed with her head against Fenrir’s chest to recover from the rest of her orgasm while Fenrir did the same.

The experiment came to an end and probably with the best orgasm of Fenrir’s life. And thankfully, Serra found the kindness in her to untie his wrists from the top of the bed, finally allowing him to move his arms again.

“Thanks,” Fenrir said as Serra returned to his side. “But… how did you not—am I bad at it?”

“What?” Serra asked.

“You didn’t cum.”

“I did. Three times.”

“Wait… seriously?”

“Yeah.”

“When?”

“I made myself stay calm so that you would keep doing it since I was supposed to get off your face once you made me cum.”

Fenrir narrowed his eyes at her. “You sneaky little—”

Serra leaned forward to kiss him on the lips and cut him off before he could finish speaking.

As for Eva, she was content simply resting atop his chest. “I don’t even care that you’re all sweaty. I’m too tired.”

Fenrir placed a hand on the back of Eva’s head to pet her. “It was fun. Thanks. And you’re good at the whole dominant scientist thing.”

“I think I need to practice some more.”

Serra rose her hand. “I volunteer for both roles.”

“Yeah,” Fenrir said, “if you ever need to practice anything lewd, Serra is your girl.”

“Maybe we could practice on Cass,” Eva said.

Serra smirked. “Yeah. We have to. Test to see how many licks it takes to get to the center of her… orgasm?”

Fenrir and Eva both tilted their heads.

“You don’t know that reference?”

They shook their heads.

“You both need to research old media more. We need to go on a binge of old movies and commercials. They don’t make commercials like they used to.”

Fenrir poked Serra’s nose and said, “I don’t know how you do it, but you always manage to make yourself sound like an old man.”

“You have a nice butt, young man. Let me touch it.”

“I’m never letting you touch any part of me again. Ever.”

Fenrir might have said that, but he was immediately disproven when Serra rolled over onto him and purposely sprawled her limbs out to take up as much space of his body as she could without getting in Eva’s way.