Responses
Who was the girl
From what I can gather I think it's just his hallucination.
I'm a few too many years late in replying, but when you read the author's comments on the chapters, you can infer that she might be a ghost or something - the author wrote something along the lines that "maybe with such superior eyesight, they can see things that we can't" (in reference to that insect that was mentioned)
http://www.mangago.zone/read-manga/franken_fran/mh/v02/c008/22/
Who I'm was the girl?