It's hard to say exactly. Maybe there was a hidden plot twist or a secret they discovered that made them run. Maybe they were trying to avoid being caught by some villains. Without more details from the visual novel, it's tough to be certain.
Euphoria isn't a true story. It's a creation of the writers' imagination, although it may touch on common issues and emotions that many people can relate to in real life.
Euphoria visual novel is a kind of digital storytelling medium. It combines text, images, and sometimes sound to create an immersive experience for the reader. The themes and content can vary greatly, but they aim to draw the audience into a fictional world.