It could also be the sound of a monster or a demon that is lurking in the shadows. This creature might use the 'po po po' sound to disorient its victims. Say, it lives in an abandoned place and when someone enters, it starts making the 'po po po' sound to create fear and confusion before it attacks.
Well, perhaps in the 'lethal winking scary story', the winking could be a signal of some malevolent force. It could be that whenever someone winks in a certain way, it triggers a series of terrifying events. Maybe it's a curse that spreads through this unusual form of communication. However, without reading the story, this is all just speculation.
The lethality of succubi in fiction really varies. It could be that in one story they're extremely dangerous and fatal, but in another, they might just be a source of temptation without being directly lethal.
A monster might be in a 'po po po scary story'. For example, a monster that has a strange way of communicating, like making the 'po po po' sound. It could lurk in the shadows and when it's close, it makes that noise to terrify its prey.
Once upon a time, in a small, old house, there was a strange noise that went 'po po po' every night. It was a doll. Its eyes glowed red in the dark and it moved on its own. Every time it made the 'po po po' sound, something bad would happen. One night, a girl woke up and saw the doll right next to her bed, making that terrifying 'po po po' sound.
In a small village, there was a well that made a 'po po po' sound. The villagers were afraid to go near it. One curious boy ignored the warnings. He peered into the well and heard the 'po po po' louder. Then, he saw a hand reaching out from the well. He tried to run but his feet were stuck. The 'po po po' was like the call of an evil entity from the depths of the well. Just as the hand was about to grab him, his friends pulled him away.