There could be a powerful magical entity that sees Sans' transformation as an abomination against the natural order of the Undertale world. This entity tries to reverse the transformation, even if it means harming Sans. It doesn't understand or care about Sans' personal journey and just wants to enforce what it believes is the correct state of things.
It could be another monster who is jealous of Sans getting all this new - found attention as he turns into a human. This monster might try to stop the transformation process or make Sans' life difficult in his new human form.
It could be another monster who is jealous of Sans' new form. This monster might feel that Sans is getting special treatment or opportunities because he's now a human. So, this jealous monster tries to find a way to either turn Sans back into a skeleton against his will or make his human life miserable by causing trouble for him in the human world, like spreading false rumors about him.
Well, one possible plot could be that Sans discovers a mysterious magic spell or artifact that gradually transforms him into a human. As he changes, he has to deal with new sensations like feeling pain and hunger in a more intense way. He also might struggle with how other characters in the Undertale world view him now that he's different.
Perhaps an evil mage who actually intended for the transformation to go wrong on purpose. They might want to use Sans' new female form to cause chaos in the Underground. They could be trying to manipulate Sans into doing bad things or using her to get to other important characters.
Dr. Eggman would be an obvious choice. Since Sonic is now in a more vulnerable human form, Eggman could see this as the perfect opportunity to finally defeat Sonic and take over the world. He might come up with new devious plans, like creating robots specifically designed to target a human Sonic.
It could be a power - crazed human general. He might have a deep - seated hatred for monsters, believing them to be inferior. He ignores all the attempts at peace and drives his troops into battle against the monsters, determined to wipe them out.
Perhaps there could be a jealous teacher in the school where he starts working as a human. This teacher is threatened by Koro Sensei's popularity among students, even though he's now human. So, this teacher starts to spread rumors or create problems for him to get him fired.
Maybe in the fanfiction, there's a scientific experiment gone wrong. A human scientist was trying to find a way to bridge the gap between humans and monsters. Sans, being a curious skeleton, volunteered to be a part of the experiment. However, instead of just creating a connection, the experiment transforms Sans into a human. As a human, he experiences new emotions more intensely, like hunger and fatigue, which he didn't really have as a skeleton. He then uses his new human form to try and convince other humans that monsters are not to be feared.
No. The Undertale community is mainly about positive things like friendship and hope. Abuse of any character, especially in a fanfiction, goes against the values of the community.
From Undertale, characters like Sans or Frisk could be main characters too. Sans, with his laid - back yet intelligent nature, could provide a great contrast to Error Sans. And Frisk, being the human with the ability to reset and change the course of events, would be crucial in any plot involving the two different universes colliding.
Well, the new human is obviously a main character. They bring a fresh perspective and set of actions into the world of Undertale. Then there are likely to be some of the well - known monsters like Sans and Papyrus. Sans with his laid - back yet mysterious nature, and Papyrus with his over - the - top enthusiasm. They often interact with the new human in various ways, creating interesting storylines.