(Sans POV [Yep early Sans Pov. He is the easiest other than Frisk for me])
He waited till he could hear the sound of the water before walking from the room, his cheeks bright blue as he walked to the front door. Before he opened the door, he shrugged out of his jacket and tossed it to the floor, needing the cold to shock his system. Whatever the river person had said really worked Frisk's mind for the poor human to forget a guy was in the room as she pulled lacey underwear out of her bag. Especially a guy like him, his imagination taking off the moment he saw the flimsy cloth in her hand.
He walked out, stepping into the snow and shivering slightly as a cold breeze flowed over his exposed bones. He stood there for a few moments, letting himself calm down as he mentally chided himself. 'What the hell is wrong with me? She is going to reset very soon. I can't let myself get like this. She needs my support, not me acting like an idiot.'
Finally, he turned around and walked in, shivering slightly as he picked his jacket off the floor. He started to the stairs, yawning and almost excited to get some sleep when he heard actual singing echoing from upstairs. Quietly he climbed the steps and went back into the room, getting close to the door to listen to his human singing while she showered. A soft laugh as he heard the lyrics, knowing the song was one of her favorites from some human band named Nirvana. He leaned against the door, humming for a moment before he began singing with her, his deeper voice actually matching her higher pitched one easily. He heard the water turn off behind him, her voice still coming through the door as if to keep up their duet, a thought that brought a smile to his face.
"Yo, Frisk. I would love to keep singing but I'm gonna fall asleep in a bit. Which where I am standing means I will get to feel what tile meeting skull feels like."
"Then go lay down, silly bones. I am almost done. Just gotta brush my hair out."
"Aww but what if I fall asleep first?"
"Wouldn't be the first time Sans. Go to bed."
He laughed at the hidden laughter in her voice before he forced himself off the door and dragged himself to the bed in the opposite corner of the room. As he climbed in he made sure to stay near the edge, wanting to make sure that if she climbed in or out of the bed he would know. Despite her assurances about Chara he couldn't help but feel worried, knowing that the spirit was probably why he was so sure about the possible dreams he could have had. As he lay there thinking he heard the bathroom door open, pulling him from his thoughts and his gaze to Frisk as she stepped out. He almost chuckled as he noticed the nightgown that had been picked went to the floor, not that the flowing material actually hid more than Frisk's skin.
"Did Toriel really pack you something that looks like a grandma should be wearing it?"
"Yeah…... Mom bought me this for a sleepover to Alphys and Undyne's place. She was adamant that there was a chance you and Pap would come over, and she thought I should be covered. Not that a pair of pajama bottoms and a t-shirt wouldn't have covered me." She laughed as she spoke, her hand tossing her brush onto the duffel bag as she walked over to bed. She frowned at him, bringing a grin to his face.
"Sorry kiddo. I get the edge so you can't escape without waking me."
"Sans …. That's too cute." She blushed as she spoke before she climbed over him to lay down. The act of her doing so gave him a reason not to lay down before her again, her nightgown riding up slightly. The little bit of skin on her legs that was shown wouldn't normally have affected him, if not for the fact her legs slid against his, the softness of her skin against the smoothness of his bones bringing a small shiver through him. Luckily for him she seemed too be tired to notice, her body curling up against his the moment she laid down. His arms wrapped around her as his eyes closed, a small part of him wondering how much longer these moments would last as he drifted off to sleep.