Some Background Information.

Petra Gurin, a girl who was found on December fourth by herself from researchers, she was revealed to be the last of her kind and now grows to adjust to human civilization. She was introduced to V-tubing, anime, and video games as a way for her to learn about the world and what's popular. Her imagination goes wild, and you'll se from there.

This was based of a SteveSekai Theory. Please watch his video on Nijisanji lore to get a better grasp on what I mean.