I don't think any of them wanted Himemiya -- the girl. Except Tenjou-san was friends with her and Miki had a crush. Plus, Tenjou-san thinks she's a prince and going to save everyone. Everyone else wanted whatever was in the castle. Eternity, I mean.

And it's all voluntary. I think the Chairman and Himemiya find out what it takes people to stay in. What they want. No one makes anyone do anything.

I left. I even was working on transferring schools. Then I ended up here.

-- Nanami