How did Gentarou get in? The cat was trying to break her way in but couldn't, and he was suddenly already in the locked room. If there was another way in, why try to break the glass door?
I guess that makes sense, especially if he's the cloaked figure in the next chap who was around before the gate + could disappear. Though, then I'd have to wonder how the glasses cat got in too before the other cat opened the glass door, unless he can teleport people with himself.
I did felt it was strange translation refered to her as "he" and stupid cat said she might be in men side of the bath, so I considered the possibility it was androgynous boy.