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Muscles on the Mind

Summary:

Oh no, Alphys thinks. She’s zoned out again. She promised herself, begged and swore and pleaded with herself, she’d stop doing that. They’ve been together long enough, she thinks, surely Alphys can’t keep finding new parts of Undyne’s body to dedicate all of her brainpower to instead of the conversation at hand.

So far, her hypothesis hasn’t been panning out.

Or, Alphys loses her train of thought.

Notes:

This fic is based on the following prompt by arsquare on Dreamwidth: "Empty-mindedness". Decided to interpret it with some tooth-rotting fluff!

This is one of many fills of mine for the Yuri Shipping Olympics 2026, which is currently ongoing! If you're interested in writing any sapphic or enbian ships for the Deltarune fandom, or any others, feel free to come along and join! You can find more information in the sign-up Google Form here!

Work Text:

“Sooo, what do you think, Alphys? Think we could pull it off?” 

 

Undyne smiles one of her iconic shark-toothed smiles (god, the things those teeth could do to Alphys) and shifts, her well-muscled arms flexing through the trapezius and biceps from resting atop her head to fold politely atop her lap. This is clearly a break in the conversation, a point where Alphys should be saying something. 

 

Oh no, Alphys thinks. She’s zoned out again. She promised herself, begged and swore and pleaded with herself, she’d stop doing that. They’ve been together long enough, she thinks, surely Alphys can’t keep finding new parts of Undyne’s body to dedicate all of her brainpower to instead of the conversation at hand. 

 

So far, her hypothesis hasn’t been panning out. Maybe it was time for a formal study. Something Mettaton could report on. BREAKING NEWS: LOCAL FISH LADY TOO SEXY??? SCIENTIST SAYS YES! 

 

Still, something deep inside Alphys—maybe shame, maybe hubris, probably both if she’s being honest with herself which her therapist has told her to be—refuses to admit defeat yet. She just has to string a few words together. How bad could it be? 

 

“Ummm, yeah, t-that sounds great, Undyne! We’d just need to, um, use my, uh… super-special science tools. Yeah.” 

 

Undyne leans forward on her hands, looks at Alphys like she’s the prettiest thing she’s ever seen. Which Alphys knows, categorically, is wrong. Undyne’s seen herself in the mirror. 

 

“Sure, babe, sounds good. Which ones should I grab for you?” 

 

Augh! It’s a trap! Alphys imagines herself stumbling back, struck by the weight of such an anime betrayal, and kneeling in defeat. 

 

“You’ve bested me once again, Undyne… but you won’t beat me next time,” Alphys quoted from Season 4, Episode 13 of Mew Mew Kissy Cutie, swooning in her chair. 

 

“HA, I KNEW IT.” Undyne pumps her fists in sweet, sweet victory, and stands to press a kiss against her love’s brow. Alphys’s tail wags against the open back of her chair, silently pleading more, more, more. Undyne indulges her, peppering Alphys’s face until she’s overcome with peals of laughter. 

 

This is what she loves about Undyne: the way she’s never gotten mad at Alphys once, even when she loses her train of thought or goes on tangents or loses focus altogether. Undyne accepts everything about Alphys, and Alphys certainly, greedily accepts everything about Undyne. 

 

“But wait, babe, you’ve GOT to hear this idea again. It’s for a SWORD you can use to cut bread, but you can ALSO set the sword on fire, so you can TOAST THE BREAD with it too!!!! Isn’t that the most badass idea you’ve ever heard?????? Isn’t your heart RACING????” 

 

There was no doubt that Alphys’s heart was.