For your sin (Story)

One day, a force called Chara destroyed the two races, Sans joined Undyne and Papyrus to stop Chara but failed then Chara smiled and said "Look, oh my! judge yourself!!!".

Sans then fainted, which angered Undyne and yelled at Chara "Damn it! how can a child like you do such a thing!?" Chara replied "Who knows haha~". Undyne transforms into a second form called "Hero of Perfection". Undyne immediately said "Now, until you die!" Chara just smiled and attacked Undyne.

The critically injured Papyrus assists Undyne but is soon killed by another Chara, causing Undyne to go into shock and scream "What the hell! This isn't a clone or an illusion, it can't be. ..." Undyne's expression was so angry that he attacked both Chara furiously. The two Chara didn't dodge either, the two Chara said at the same time "My my! you can't tell the difference, it's like it's both reality and fiction mixed together", after a while of fighting Chara got bored, so she used his hand to hold it in the air and then tore it open, creating a tear in the boundary between nothingness and reality. Undyne then blows both Chara away then closes the gap and says "I don't know what that is, I don't care who you are or anything, I just need to know you can never be defeated The real thing has the most perfect body and I never lose because everyone is hoping for me to protect everyone's dream!!!".

Chara started to turn black and said "Oh yeah...that's ridiculous", Chara raised her knife and slashed through the air once, everything around was torn apart including the second Chara. Undyne parried this attack from Chara. Chara said "Very surprising, if only you were my ally to deal with Yama Gaster", Undyne didn't care but Chara's slash destroyed the system in the temple of sages.

Undyne was surprised and said "Wait, where is this? I didn't think it would turn out like this, if so now you're stuck with me forever! Anyway I've got nothing left to lose, everything All have been destroyed. My house, my friends, everyone and this immeasurable world have been destroyed by you!!!" Chara is disappointed and says "It's not like I'm stuck you idiot, you never know what I am but basically as you can see, I'm the embodiment of pure genocide so I don't have any can destroy me, I am not bound by all concepts related to obliteration and death because I have always been outside of it even more. Well, now this place is completely destroyed, everything the idea has also disappeared, all parallel multiverse infinite sea chains have been destroyed....that's all, now let's go somewhere else".

Chara is about to disappear when Undyne screams and throws Sans at Chara and says "I hope for you, Sans remember to stay alive and don't forget me, I will wait here until you come back because you alone are the smartest person in this world, you will surely find a way to recreate this world and everything so good luck Sans!".

Then Sans and Chara malfunctioned after Undyne throws Sans at Chara, both then disappeared and left Undyne alone in a place where there wasn't anything, now it's just an empty world and Undyne continues to sit here and did nothing, for Undyne knew nothing beneficial could be done at the moment.