Chara has the scary ability to jump into savefiles and corrupt them by taking over the fallen child and making them do a 'Genocide Run' When Chara comes across a continuing timeline that has reached the surface but has not yet been reset under the name of 'Frisk', curiosity takes over and they leap into this save file...
Chara has been reseting the timeline over and over. Frisk can only watch helplessly as she is the property of Chara since she sold her soul. However her friends appear and with the combined might of Humans and Humanity they create a new timeline, erasing the old one. A new timeline free of PLAYER.