Terezi let out a low set of moans as Karkat's bulge tried to writhe around under her. She gasped softly at every movement, letting herself feel every little movement, concentrating on the beautiful red smell of the room. Karkat could only blush and bite his lip as Terezi grinded her body firmly against his bulge, and quickly up and down it, stroking it softly with her undergarments which felt soft and all the more enticing to him. He moaned as she came to a stop, still resting her body firmly on his, her soft and curvy framework tight against his own. Karkat looked over Terezi's body, glancing deeply at her luscious form, her distinct and mellow shape. He sighed in a sort of content bliss as he heard Terezi moan softly, her body heaving from her continued experience. She cackled again and swung her head forward slightly, glancing deeply into Karkat's eyes.
"SO, YOU 3NJOY1NG YOURS3LF? 1 M34N, 4S MUCH 4S YOU C4N WH1L3 B31NG T13D UP 4ND UN3FF3CT1V3 4T P3N3TR4T1NG 1NTO MY S33D FL4P. WH1CH, 1F YOU H4D NOT NOT1C3, 1S R4TH3R ST1MUL4T3D NOW, TH4NKS TO YOUR SH1NY R3D NOOKSN1FF3R BULG3."
Terezi cackled and Karkat sighed, blushing intensely. Terezi leaned down and licked his cheek softly but passionately, remarking on the "R3D" taste. Karkat panted softly and distracted himself by looking back over Terezi's body. His eyes were directed down to her crotch, where he lace and deeply red panties were. They looked tight on her aroused seed flap, which he could see hints of through the semitransparent material of her underwear. Teal genetic material was leaking out of her flap and onto her panties, but pooling a bit onto her thighs as well, caking onto her skin. Karkat blushed even deeper, if that were somehow possible and moaned as he bulge squirmed again. Terezi cackled and rubbed his bulge with her seed flap and her soft and yet erotic hand movements.
Karkat's breath hitched as he panted, feeling a release coming ever closer, Terezi's breath hitching too as she felt the same way. They both shook softly and moaned as they thrusted their hips in synchronization, their movements getting faster and faster until they both came, genetic material spraying onto each other's thighs and chests and onto the bed. Terezi cackled low and long as her movements slowed down, Karkat's movements still a bit fast.
"K4RKL3S, WHY 4R3 YOU STLL MOV1NG? ST1LL W4NT 4 L1TTL3 B1T MOR3 FOR TH3 MOM3NT?"
Karkat nodded as he brought his hips to an abrupt stop, he bulge shaking and still writhing in front of Terezi.
"HMM, OK4Y. L3T M3 CL34N UP 4 B1T F1RST 4ND TH3N… TH3N W3 C4N CONT1NU3."
Terezi blushed as she pulled her hands up her chest and then Karkat's, smearing the slew of genetic material all over him. He gasped softly and moaned as he inhaled the pheromones and endorphins in the room, now all closely smeared on him. He struggled to break free, to taste of these things, but he was still tied up as Terezi walked away, her hips swinging, her body bouncing as she went to go clean up a bit, to get ready for some more Christmas "presents".