Going through Waterfall was hard. He was thankful for the jacket that Papyrus left. It kept him dry from water. He would have gotten 'soaked' to the bone. Sans ignored the area mostly because all it reminded him was being chased by Undyne until he heard a hauntingly familiar tune. It was the music box. He remembered that Frisk wanted to dance to it, despite her having a hard enough time standing. He covered his mouth to stifled a sob. It was his first dance with Frisk and it was also the first Save Point where he held Frisk when they had to RESET. Each time, Frisk looked more tired and determined than the last. He couldn't believed that his sweetheart had the guts to keep going. He closed his eyes and remembered.
He felt Frisk hands holding tightly onto his boney ones, muttering to not drop her. He laughed as he kept a tight grip on her. "I'm not gonna let you go Sweetheart. I'm not that cruel." Frisk gave a happy laugh.
"I hope so, it's so nice to be able to dance. Even if it was just for a little bit."
"If you ever need to stop Sweetheart, just tell me. I don't want you to get hurt." Sans reassured her, trying to make sure she doesn't collapse on him.
Knowing that Sans is worried for you, fills you with DETERMINATION.
Sans opened his eyes, the music still playing softly. He let his arms fall back down to his sides. He took a keep breath and left, whipping the tears away from his eye sockets.
He continued walking pass through Waterfall. Sans couldn't believed all the beauty he missed. Frisk had always took time to enjoy the beauty of Waterfall. He kept worrying about being caught or worst. He notice things he didn't notice before, such as a lonely echo-flower. He took a few steps and allow it to play.
"I wish Sans would stop worrying about me and be happy." His breath hitched, but he covered his mouth so he didn't make a sound. He didn't want to leave. He fell to his knees and listen to the echo flower. After what seemed like forever, he got up and started walking away. He had to keep going. He had to let his little flower know that she can do that. He had to get on with his life. Of course, first, he had to get to where his sweetheart became fully blind.
He looked right up at the entrance of Hot Land. He couldn't forget this place. Oh, how did his dear Frisk beg not to kill Undyne right then and there. That had to be the hardest thing for him. Undyne had been chasing them for the whole time. He had to keep his head down or he would be called a traitor, but after all the times she killed Frisk and himself, he didn't care. They just kept trying and trying to be friends with her. Each time they died, they would respawn back into his arms. Where Frisk knew they was safe from harm. The last time he died to Undyne because he got in the way of him killing Frisk, was the last straw for him. He was about to kill her when Frisk begged him not to kill her. Oh, how did he wanted to murder Undyne right then and their, but that begging was what made Undyne like her. Frisk was passionate about what they did. Frisk then begged to go visit her to see if she was alright. "Drinking Tea with your Murder" sounds fun, doesn't it? Frisk didn't seem to mind. They continued By this point, they were fully blind. This was the only saving grace because it didn't effect their walking too much. He knew that it would be a matter of time.
A matter of time before they reached Asgore.