[@BrokenPromise]
They have been a well-kept secret for the most part, but there have been sightings, yes; occasionally a glimpse of a magical girl or a lurking monster has been seen, but these cases have either been assumed to be products of imagination or too unbelievable to be true. The hospital attack may cause a heightened awareness in weird activities, however.

There is a website dedicated to weird sightings, and they include descriptions of young girls wearing weird outfits running on rooftops, but nothing more; people think it's just cosplaying kids being overenthusiastic.