Aswang is not one monster but a name that gathers several. The blood-drinking manananggal, the tik-tik that lowers a thread-thin tongue through a roof to take an unborn child, the corpse-eater, the were-dog, the witch — all fall under it. The name appears in Spanish missionary records as early as the sixteenth century.
What unsettles is not the shapeshifting but the daytime. By day an aswang is entirely human, and usually turns up as the quiet neighbor who keeps to themselves. The tells handed down are correspondingly small: a reflection that shows you inverted, a tongue too thin. In the Western Visayas, and in Capiz especially, the belief is still living.
In a story where one of the neighbors is the thing, there are ways to check and nothing to undo by checking. The moment you have the eye for it, every neighbor looks different.