Thinking about it a bit more, maybe Pomni being an urban explorer is fitting. Something that jumped out at me in the first episode was Pomni going through the exit door when it reappeared because it wasn't something I would've done. I would have been too scared to go through on my own and I'd rather potentially miss my chance to escape than get stuck somewhere alone. I imagine urban exploration being a hobby where if you see something weird you just get out. Earlier, when she entered the circus, the first thing she did was run towards an exit. When an abstracted Kaufmo attacked Ragatha, she got out of the way and stood back to watch. I think she had such a big freeze response because she was fighting every instinct in order to not leave someone behind. The way she looked around the circus in search of Caine made her seem like a natural too.
In episode two, she fell into an out-of-bounds area and she was level-headed enough to grab onto one of the floating objects. When she landed, she seemed mostly uneasy because of Gummigoo's panicking. After talking to him, she got right to work in finding a way out. In episode 3, while being pretty freaked out, she kept her goal set on finding a way out. She tried to walk through a cloud of souls even though she was warned twice.
So Pomni has a reserved personality but is brave enough to explore abandoned buildings? It feels contradictory. It's possible we misunderstood her behavior during the initial shock as social anxiety when she might have acted differently in real-life. Or the fear of people and the fear of a dangerous environment could be completely separate for her. Maybe Ponmi finds reassurance in being able to navigate an unknown place. Reassurance that would be hard to get in social interaction.
I also want to point out how she looked when she shared she was an urban explorer.
[ID: Pomni speaking at the bar scene. She's looking to the side and has her hand on her other arm. The subtitles read "-and I would seek out mild thrills." End ID]
She seemed ashamed which was a little weird. I wouldn't know but in a casual group I thought these kinds of hobbies would be looked at with intrigue despite their danger and legality. It does seem out of character, so maybe she was embarrassed because of that?
[ID: Pomni in the same scene looking down into her drink where her face is reflected. She has a finger on the rim of the glass. She says, "It was just something I did for me." End ID]
It feels significant, but there are many ways to interpret her reaction. What I thought was that she was lying with a partial truth about her reasons for going into the C&A building.