Not exactly a Sanscest oneshot but I decided to post this anyways

 The purple skeleton curled up in a ball and wept as the harsh words that were spoken earlier to him replayed in his head. He wasn't bad... just because he took care of the dark apples didn't make him a bad monster. "Dream..." he sobbed his twin's name over and over again. Wanting his brother to return already. But no matter how many times he called out for his twin's name, he never showed up. His soft cries filled the surrounding areas. After what seemed like hours to the negative guardian, Nightmare let out one last sniff before wiping away his tears. Calming himself down, Nightmare took deep breath's in and out. Rays of the sun shown down on him as he looked up at the spotless blue sky. A warm breeze passed by, and the skeleton listened to the rustling of the leaves. Tearsmarks stained his cheeks still, but he knew he could get rid of them before his brother returned. He closed his eyes and listened to the birds chirping. The purple guardian let out a small smile at the peacefulness around him. Opening his eyes, he turned to look at the village. He couldn't help but frown at the sight. "I...I wish they never came here..." the crowed skeleton thought, "Everything had been fine before they came." It was just Dream and him protecting the tree. Just him and Dream... no one around to hurt him. Nightmare looked at the yellow cape that was tied around the Tree. He ran his hand across the cape. Dream and Nightmare had made that cape together. They used it to cover the blood that was on the tree. "Mom..." Nightmare whispered to the tree, "What should I do...?" He didn't think he would be able to handle the villagers any longer. The previous guardian appeared before him, her eyes holding no hate or malice. Just love. Her short green hair blowing in the wind as she leaned down to hug him. "It'll be alright, Nighty." She whispered softly. Nightmare stood there in silence before sobbing into the other.