I don't know for sure. To figure out if Millie is a real story, we'd need to know more about the plot, the source, and any background information available.
The appeal lies in its combination of fantasy elements and emotional depth. The plot keeps you engaged, and the visuals are stunning. Also, it offers a refreshing take on common themes.
Some loona fanfics focus on the relationships between the members. There are stories that show their deep friendships and how they support each other through tough times, like during a fictional concert tour where they face various challenges but come out stronger together.
Such comics usually have highly provocative and raunchy imagery. They are not in line with ethical and moral standards and are not recommended for consumption.
It's hard to say exactly as it could vary, but typically it might include detailed storylines, character interactions, and maybe some unexpected plot twists.