Sans in Heat X Reader

It had been about a year since you fell into the Underground. The monsters there were all so nice, and the humans on the surface started to seem nothing but cruel. You had made the decision to stay in the Underground. During your journey, you met the two skeleton brothers; Sans and Papyrus. Papyrus seemed... very enthusiastic. He was always so full of himself. You just went along with it. But Sans on the other hand... He always seemed so calm and collected, and you two had become quite fond of each other. In fact, you were sure that you and him were destined to be together.

Months and months passed by, and now, here you are!

You had been at a sleepover with Grillby's daughter for about a week. You had missed Sans the whole time, even though it wasn't yet confirmed that you were boyfriend and girlfriend.
As you left her house, you heard her call out to you.
"Bye, y/n! See you again sometime!"

"Bye!" You called back.

You began walking back to Snowdin. After a couple of minutes, you arrived back at the skeleton brothers' door. You creaked it open. No sign of Papyrus. He must be at training with Undyne, you thought. You closed the door silently behind you. You couldn't wait to see Sans again!

As you set down your stuff, you began to walk up the stairs. As you approached Sans' door, you could've sworn you heard what sounded like groaning.

"Sans?" You said softly.
"Are you okay?"
...
No response.

After a few more seconds, you decided to open the door. You reached for the handle, and slowly pushed it open.
"Sans-"
(Heeere comes the sin!)
You cut yourself off with a gasp as you saw Sans lying on his mattress. Sweat was trickling down his skull, and his glowing pupils were blurry. You hear him panting and groaning in discomfort. Your eyes scanned down his body until they landed on his shorts. Beneath the black cloth, there was a faint, glowing blue light that appeared to be seeping liquid through his pants.

Sans gasped as he saw you and quickly at up.

"y-y/n!" He exclaimed, clearly shocked. "i-i'm so sorry... i didn't hear you come in- i...!" Sans stammered, clearly looking for words.

You simply stood there, looking at him in shock. After what seemed like an eternity of awkward silence, you slowly closed the door behind you. You began to approach him, and sat down on the mattress in front of him, blushing.

He blushes back, clearly unsure of what exactly you were doing. "j-jeez... y/n... i'm sorry you had to s-see me like this... i..." Sans looks ashamed.

You didn't know how to respond, but you wanted anything but for him to be unhappy. "H-hey... it's okay..." you said gently. After a few more moments, you said, a little embarrassed, "C-can I help you with that?" Signaling towards his glowing member in his shorts.

Sans' eye sockets widened. He was clearly shocked. "wh-what?"

"I-I don't want you to be uncomfortable... and, I wanna help you..." you said shyly.

A few moments passed. You were afraid he would say no, until you heard him say, "a-are you sure?"
"Definitely" you replied, even though you had never done this before.

"o-okay..." Sans said. "as long as you're okay with it."

You nodded in confirmation. Sans relaxed, and you smiled at him. You then carefully lifted up his shirt, revealing his pristine white ribs. You then gently placed your fingertips on his sternum, and glided them up and down.

"H-hh..." Sans let out a hitched breath as he shivered at your touch.

You smiled at him again, pleased that you were making him feel good. You then trailed your fingers over to his middle left rib, and slowly wrapped your fingers around it. You began stroking your hand around it from side to side.