https://www.tumblr.com/dragqueenstarscream/779570452984102912/cant-stop-thinking-about-the-seraphina-prime-au
It comes out on accident. Not to say he doesn’t mean it. He’s said it before, buts it’s always been for Sera. When he’s been between her legs, when she’s been down on her knees, or when she’s on top of him. He’s called *her* that. Never Sentinel.
And Sera had adored it. So makes sense to see Sentinel enjoy it too. But maybe there’s something different about being called that when it’s Sentinel and not Sera because once the words slip into the air he feels Sentinel’s thighs press into the side of his head, more liquid than ever before gushing onto his tongue. Sentinel’s. Legs shaking and his optics squeezed shut, a whining cry of Optimus’s designation rolling off his glossa.
Optimus has a tease on tip of his glossa, something about Sentinel’s stamina but then he looks at Sentinel’s face, blissed out, internals clearly hot enough that he’s trying to suck in air through his mouth.
Too soon Sentinel catches his breath and embarrassment flares as he catches sight of the mess of fluids around Optimus’s mouth. He opens his mouth and Optimus can feel the incoming plea for Optimus to just ignore that because old habits die hard, even with their work and secrets shared. So he stops this before it even begins.
“Sentinel? Can my good girl look at me, please?”
Widened optics catch his own and he can feel the way Sentinel’s thighs twitch under his hands.
“Good girl.” He compliments and Sentinel twitches. Optimus can see a slight wobble in Sentinel’s lower lipplate.
“You’re being so good for me. Do you want to keep going?” He asks because he’s worried, doesn’t want to overwhelm him, after his slip of the tongue.
“Yeah.” Sentinel gets out after a few kliks of trying to reset his voice box moment, “I want to keep going.”
Optimus smiles and presses his lips to Sentinel’s inner thigh. Enjoying the way his breath his voice hitches.
hooooooly SHIT THIS IS SO GOOD
the love shared between sentinel and optimus, optimus being so caring when he sees something's up with sentinel, sentinel enjoying being called good girl outside of seraphina, possibly from gender euphoria, possibly from optimus inadvertently showing that he accepts both sentinel and seraphina as the same person... my GODS, this is SO GOOD! THANK YOU