I have seen many times in anime and manga that a character eats his/(mainly)her lunch in a toilet.
Examples include Nagisa from Kanojo mo Kanojo who used to eat her lunch in the restroom. (Revealed in Episode 3)
Another example is Yuria from Mieruko-chan, who is caught by the MC eating sitting on a toilet. (Revealed in Vol.3 Chapter.17)
Why do characters in anime/manga eat their lunches in restrooms? Is this kind of behaviour a meme in Japan or due to some special culture in Japan? How common is this practice in Japan?
Besides, I noticed the characters involved in such behaviour seem to have one thing in common: they are introvert and don't have many friends. I am not sure whether this common trait have anything to do with their choice of restroom as a place for lunch, though.