Hi, I'd appreciate it if you could explain what q Chan is, I'm still confused
Just a ghost. The food eating and things are all
reference to the Q-Taro manga. Since basically everything in this is a Doraemon/F.F's works manga.
Ghosts happen when a soul goes back into the
same body, the "cloth" of a ghost is actually skin that's super regenerating forming a sheet. According to Obitto in chapter 48. This is why Yoki asks if Q is Futaha, because for the memories have to line up, it would be Futaha's soul back in the same body. (Which probably couldn't happen because in Chapter 40, the mice believe she killed herself in the storage room after being placed in the draw and shot back outside, and had no idea she was going into the Vivarium. interestingly the only real big volume/magazine change was about adding an extra box where Yoki says that the ghost will be called "Q" after Kikkuri say's Nodoka-chan, I guess because he decided on the Hemmingway twist afterwards.)
The word the rats used for "remains" is like leftovers/dredges. Super literally it is was something like ~ fragments of the dredges of Futaha~, not remains in the way like a person's ashes or whatever. I
All the ghosts have seemingly inherited bits of Kaiba when she died in the Vivarium, I guess she was experimenting on them so it passed or maybe the outside/upper people DO have souls. We don't really know.