Your fate was already sealed from previous timelines. You were the first and only human attempt by Gaster. You were not perfect as he thought and Frisk and Chara taught you some things to learn how to be normal, to learn how to be a person.

After Frisk's death your fate was placed back in the hands of the scientist who, in order to focus on the strongest one, Chara, forced him to do the same to you as he did to his brother by staining the hands of the then child with the blood of the people he loved most.

Tears were falling on the cheeks of that child version of Chara. With your last words you promised him to come back but maybe it was not the way the white-haired man wanted it.

—

Gaster created a new timeline, this time it was a test one where there were some experiments going around in that town of Xtale like monsters and humans that was once Chara's home.

Chara walked for a few minutes among the streets with people but stopped when he heard a familiar voice in one of the houses. It was you.

He knew that voice as he followed it, and he could finally see you talking to your friends. You were the same person as he barely remember even if everything was different but for some reason Chara was waiting for you to remember him...or maybe not.