In chapter 52, the ghost Ranko can be seen spray painting some graffiti on a wall. The phonetic pronunciation of the kanji symbols is yo-ro-shi-ku, “yoroshiku” meaning "Hello!" or "Best regards!" (among other things). Taken individually however, the kanji symbols have perhaps darker meanings when taken together. They are, from left to right, "Night – Dew – Death – Pain." An English equivalent might be, "Hell Oh!"
This is obviously not the real meaning of "Yoroshiku" but a pun and playing around with kanji that have similar pronunciation but different meanings.
RIN-NE readers that have been with us since the beginning will recall seeing this on the damashigami rabbit's T-shirt in Vol.1, Chapter 5.
I still want that T-shirt!