I assume this is the first mention of Hana, who she is isn't really important. All we need to know is that she was one of the kid slaves they brought, who decided to run away after training, and serves as a way for the other kids to talk about how Mikoshiba isn't forcing them to stick with him and end up resolving themselves to working under him.
It's a little weird that we don't even get a few panels referencing Mikoshiba's recovery, though.