Specters. The supernatural. Spirits, as they are most commonly called. For some, there is a staunch belief that beings from beyond still roam the Earth. The idea is that they physically cannot manifest as their corporeal selves. However, through their ghastly ways, it is possible to feel their presence or hear their meddling.
Kyoukai no Rinne is an anime about these very spirits. Good spirits, bad spirits, spirit whisperers, spirit exorcists, and so on. The show is replete with spirits of all shapes and sizes, all backgrounds and creeds. While not necessarily spiritual, the amount of spirits is undeniable.
I cannot say for certain if I have ever seen a spirit roaming nearby. I actually do not believe that spirits exist. But there have been occasions where I thought I saw something out of the corner of my eye or I felt like something was there that should not be. Those moments would pass quickly, so I would think nothing of them. Though thinking more about them now, perhaps that was people like Rokudou, Sakura, and the gang helping one more spirit pass on.