Alphys had no idea what had come over her.
It had started with one of those ideas one has and immediately discards; a non-idea, a spur-of-the-moment thought in which all rules of conduct and decency between monsters had not yet been factored in.
In other words, a bad idea; the kind that were better left unsaid, and even better left undone.
And still, here Alphys had found herself, her snout pressed against the sweaty, squamous abs of the monster whom had so graciously invited her to snuggle on the couch, her tongue slowly dragging across the blue scales of her stomach.
With her snout pressed to Undyne's damp skin, all she could smell was sweat and fish – the former a common aroma in the house after the redhead's workouts, which were similarly common, and the latter so prevalent that Alphys had gone almost entirely numb to it. Almost. With every salty drop which kissed Alphys' tongue, the scientist's trembling claws clasped into a tight ball at her side, her heart racing in her chest until the moment her flexible muscle finally lifted away, a near-silent sigh escaping her lips.
And in its wake, a silence that could undoubtedly be heard from the surface.
By the time Alphys' brain had finally managed to process exactly what she'd just done, the saurian woman had frozen up entirely, her eyes wide as she stared at Undyne's stomach, some of her scales now shimmering with the thin layer of saliva Alphys' tongue had left behind, contrasting the shimmering beads of sweat that remained.
Once again, Alphys had no idea what had come over her.
Well, beyond a genuinely bad idea.
For a moment, Alphys considered what her chances were if she were to simply never look up; to remain here, forever, perpetually staring at the muscular stomach of her girlfriend. It sounded like the same sort of logic used in dinosaur movies, and considering she was a dinosaur herself, she knew all too well that such logic was tragically flawed.
"..U-Uh, Alphys?"
Undyne's tone caught Alphys off-guard; being as accustomed to the other's boundless confidence as she was, it felt strange to hear her speaking delicately, her voice tinged with surprise. Of all the emotions in her voice, however, Alphys didn't notice anything close to anger – a good sign, if anything about this situation could be considered remotely good.
Steeling herself, Alphys began to lift her head, looking up toward Undyne with an ashamed expression across her snout – only to be promptly shoved back into Undyne's abs by a strong, incredibly familiar hand.
"You missed a spot, nerd." Undyne mused, her hand slowly stroking Alphys' crest as she kept her snout flush to her stomach. "So," Her fins shifted to match the curious expression spreading across her lips, "is this one of those things you've been meaning to tell me you're into?"
Though she couldn't see it thanks to Alphys' current position, she certainly felt the intense heat coming off of her as the other girl's entire face flushed beet red, the smaller monster shivering as her tongue slipped out once again, lapping against Undyne's sweaty skin at a slow pace, only to find herself licking more eagerly as Undyne continued to pet the top of her head.
Truthfully, the thought had never crossed Alphys' mind before; and yet, here she was, chubby legs beginning to fidget and squish together in excitement as she pressed gentle kiss after gentle kiss to the other woman's abs, tail beginning to ever so subtly wag beneath her labcoat.
"Yes.." She finally gasped out, rubbing her snout gently against Undyne's stomach.
Alphys didn't quite hear it, seemingly too enamored by this new discovery of hers to notice it, but Undyne breathed out a sigh of relief at her' response, relaxing against the couch with a blush of her own spreading slowly across her face.
She was relieved she didn't have to tell Alphys she'd been wanting to try this.