Who could be the main characters in 'sans becomes a girl fanfic' besides Sans?

Papyrus would be a great addition. His relationship with Sans could take on a whole new dynamic when Sans becomes human. Papyrus might be overprotective at first, not sure how to deal with his now - human brother. He could also be a source of comic relief as he tries to understand human behaviors.

In a 'sans becomes a girl fanfic', perhaps Sans - now a girl - decides to use this new form to her advantage. She could try to infiltrate a group that was previously only male - dominated in the Underground. This would lead to a whole series of adventures as she tries to keep her true identity a secret while achieving her goals.

Alphys could be another common character. As the royal scientist, she might be called upon to figure out what's wrong with Sans. She could bring her scientific knowledge to the table, trying to diagnose and find a cure. Her own insecurities might play a role here too, as she might be worried about failing to help Sans.

A love interest who breaks the girl's heart can also be a main character. His actions, like cheating on her or suddenly leaving her without an explanation, can be the catalyst for her transformation into an evil character. Then the story could revolve around her trying to get back at him in devious ways.

Pikachu would definitely still be there. It's Ash's most loyal companion, and it would be interesting to see how their relationship might change now that Ash is a girl. Maybe Pikachu would be more protective or show a different kind of affection.

Lucy could also play a major role. She might be the one to help Natsu adjust to his new life as a girl. Maybe she gives Natsu tips on how to dress and act like a girl, and they could have deeper conversations about what it means to be a girl in their magical world.

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.

Besides Steven, the main characters could include the villains he's faced in the past. Now that he's a girl, they might underestimate him or treat him differently. His father Greg could also play a big role. Greg might be a bit shocked at first but then would be super supportive, trying to understand what his 'new' child is going through. And there could be new characters introduced, like other girls in the town who become friends with Steven and help him adapt to the female world.

There could be a wise old wizard who tries to reverse the transformation or at least guide bpy through the process of being a girl. Another character might be a best friend who accepts bpy immediately regardless of the change and helps bpy with all the girl - related stuff like choosing outfits.

He might also interact with Rias. Rias is a powerful devil and a leader. Sans could approach her with his laid - back attitude. She might be initially suspicious of him but later come to respect his abilities. They could have some strategic discussions about dealing with common enemies in the High School DxD world. And Sans could probably crack some jokes that would either amuse or baffle Rias.