Redo
Sans woke up next to Serifa again. His head was killing him. He couldn't think of any plan at that moment, let alone fight. Realising that, in this state, he couldn't protect Serifa at all, he decided to rest.
-Serifa, my love... he shook her gently.
-Good morning Sansy... she yawned, without opening her eyes.
-I'm...expecting someone today... So if you hear the bell ringing, please, wake me up. I wanna be the one who opens the door, okay?
-Okay... she replied in a sleepy voice.
-Thank you...and sorry for waking you, sweetheart.
As soon as their conversation ended, Sans fell asleep. He really needed it, since he had used up all his energy by repeatedly going back. After a long while, the bell rang, but neither Sans, nor Serifa heard it. The bell kept ringing, until Serifa finally woke up.
-Sansy...the bell's ringing...you told me to wake you...
Sans was too deeply asleep to wake up just from that. The bell kept ringing.
-Sansy...come on, you need to open that door! she shook him.
Sans was still unable to wake up.
-Sans! she started shaking him more vigorously. Wake up!
-What is it...? he mumbled, half-asleep.
-The bell is ringing! You wanted me to wake you so that you could open the door...
Sans mumbled something, instantly falling asleep again. Serifa sighed. The bell hadn't stopped ringing.
-Should I go open? Your guest will be annoyed, staying in the cold for so long.
-Sure, go, whatever... Sans mumbled again, not grasping the situation at all.
-Alright, I'm going! You should get up too though, it's be rude to sleep when you have a visitor!
Serifa put on some slippers and left the room. Sans, being barely awake, had still not fully understood what was going on. Then, as he was ready to fall sleep again, it suddenly hit him. His eyes opened wide and he immediately jumped out of bed, running to the living room.
-SERIFA, WAI-...
He was too late. Serifa had already opened the door and the Royal Guards had stabbed her with their swords, killing her once more. Sans fell on his knees, crying with his head in his hands. Without noticing him, the Royal Guards finished collecting her soul and left the house.
-What...what should I do to fix this mess...WHAT SHOULD I DO? he desperately screamed out, as an unseen hooded figure sat next to him, ready to touch him.
He walked back to his room. The sheets had kept her smell. It felt like she was still there. Sans wrapped himself with the sheets and closed his eyes in an attempt to feel her presence again. He decided it was time to start thinking. Until now, he was just improvising. But after this timeline, everything would be thoroughly thought about.
His energy was recovered enough. He was ready.
-Alright...this time, it'll work for sure.
His left eye flashed.
He woke up in the same bed once again. He checked on Serifa. Everything was normal. He had a mild headache, but it was nowhere near the pain he had experienced before. But even if it was, he had a lot to do.
He locked Serifa in his room, not wanting to run the risk of her getting out and being seen. Then, he proceeded to leave the house. He had to find the Guards. He knew they were there, but couldn't actively look for them, since he wasn't supposed to know.
-Aaaaah, killing humans sure is refreshing! he stretched and shouted out loud, hoping for the Royal Guards to react.
Luckily enough for him, the two Royal Guards came out of the woods they were watching from, revealing their hiding place to Sans.
-Hey Sans! Did you just mention...''killing humans''?
-Yes! In fact, I just killed one. It was probably the one everyone was looking for a few days ago. I'm definitely joining the Royal Guard after this!
Sans was great at acting excited. He surprised both himself and the hooded figure watching him.
-Wow, good job Sans! We were actually sent here to kill that human. Undyne told us she had hypnotised you!
-Yes, she had, but I realised it yesterday and took care of it! he winked.
-So, where is the human?
-Oh, I already took her soul to King Asgore! Then, I returned home to change clothes. Gotta wash all the blood and stuff. he grinned.
-But we didn't see you go or come back... And the King didn't change our orders either...
-Well, he soon will I assume. He said he had to take care of some business first. Why don't you go check it out yourselves?
Sans was starting to get disgusted of how easily he could mention killing Serifa while smiling and pretending to be happy. But he needed to do it, if he were to save her.
-Let's all go together then! I'm sure you'll become one of us today Sans! We have to celebrate!
-Umm...no need to do that...I mean...I have stuff to do today...
-Ain't hearing anything! We will all go to the castle and celebrate!
Not having another choice, he followed them to the castle. That complicated things. In his original plan, they would go to the castle without him, giving him time to warn Serifa to hide somewhere away from his house. Then, he would pretend to still be under her hypnosis control, giving him an excuse for his lie. The next step would be to hide Serifa in his house for a while. And, after the situation was forgotten, he was going to paint on Serifa's face and body, making her as unrecognisable as possible and telling everyone that this was a new friend he made. They would have to be extra careful of course, but that was the closest he could offer her to a normal, happy life.
The problem now was that he couldn't warn Serifa to leave the house. After finding out the truth, the Royal Guards were sure to look for her in there. He had to distract them somehow. He kept thinking, sure he would find a way.
And so they reached the King's castle, and the truth was revealed. Undyne scolded Sans for his naivete and wanted to imprison him for treason. Thankfully, the Royal Guards defended him, picturing him as the victim of a really cruel and powerful human.
So far so good. They returned to Snowdin, to continue looking for her in Sans's house. Sans was getting a bit nervous, still not having figured out a good way to distract the Guards. But, as they reached Snowdin, he noticed some sheets tied together, hanging from his room's window.
-Seriously...? Did she really escape through that because I locked her in? Gosh, that girl is crazy! he thought to himself.
But that actually worked for his plan. The Guards didn't find her in his house, since she had escaped. All he needed to do was persuade them to leave Snowdin and look for her at the Waterfall. After all, she wasn't likely to have gone there, so that would buy him some time to find her.
-Guys, I think you will find her at the Waterfall. She probably went that way to find the barrier. I'll look in Snowdin, just in case.
-Alright Sans, just be careful! She might hypnotise you again!
-I will guys. I've learned my lesson.
As Sans was escorting the Royal Guards out of Snowdin, he heard the worst thing possible.
-Sansy! There you were! I was looking for you!
He turned around to see Serifa running towards him. Unfortunately, he wasn't the only one who saw her. The Royal Guards lashed out to her before he was even able to attempt anything.
And that was it. One more Serifa corpse. One more blue soul stolen away. One more timeline with a dead end. One more failure.
Sans knew the cue by then. It was time. His left eye flashed.