The last chapter was kinda inspired by assassination classroom cuz I finished watching it a few days ago and (it made me cry a lot-) I thought the ending was worth writing
***
These kids had so much potential, with the way they were able to utilize their powers and minimize the side effects. They had come so far from their universes being destroyed. The three of them could attack together and separately. Sammy could reduce the amount of papercuts they got now from their papers, Ren could teleport farther distances, and Alex could ignore the side effects of floating herself for longer.
The assassins were so talented and admirable, they worked so well together and the way they reacted to each other was so natural despite the stark differences in their personalities. Sammy was shy and easily flustered, Alex was more extroverted and happy, and Ren was very introverted and preferred to not talk as much. Today was the last day of training, you were all qualified assassins working to kill XGaster.
There wasn't much training to do today, since you were all qualified to do the job you needed. Five assassins, three of which were no older than sixteen. You and Frisk were eighteen, only two years older than your peers. Error was the oldest, being twenty-nine.
~
Today was assassination day. Everyone wore black versions of their normal clothes, with Sammy exchanging their non-binary flag hoodie with an asexual flag hoodie. The plan was for Sammy and Ren to attack first, creating a diversion for Alex and Error to attack. You and Frisk would finish the job, assassinating XGaster.
Ren was quieter than usual, clearly scared. Alex tried to distract herself from knowing she would be responsible for someone's death. Sammy just drew in their notebook, tears welling up in their eyes from fear. They got out their phone, texted someone, plugged in their headphones, and listened to music with their eyes closed. They seemed to be the only one of the three who knew they could very well be killed.
* It's time. Knowing Frisk, your dad, and these kids with so much potential are standing by your side fills you with DETERMINATION!
You were in the original Undertale universe. It was time. Sammy and Ren immediately ran towards the target, who was facing another way. With the adrenaline of battle and feeling more confident, Sammy started singing quietly, as if to taunt XGaster for not being able to tire them enough to the point where they couldn't sing.
Their song, though in a language you didn't understand, seemed like a battle cry, taunting the target and daring them to try harder to bring down the perseverant human. XGaster was trapped by Error's wires, the only thing left to do was to kill him for real. Frisk sat down next to him and raised his bright red knife, hands shaking. He didn't want to do this. You sat down next to him, putting your hand over his. With one swift strike, it was over.
So that was it. XGaster was dead, all you had to do now was neutralize everyone else who could be a threat to the happy ending you had been trying to reach for years.
"W-We did it..." Alex said, in shock. It wasn't a matter of strength, it was a matter of outsmarting. But you did it. You beat him. The biggest threat to the remaining multiverse was gone.