Y'all are NOT serious about Okaasan.

▶The whole song is: "Okaasan is coming, her neck is twisting" and those guys are like "this is the scariest story ever! She is coming! And her neck is twisting! I got nightmares listening to this song!"

◇ first of all, the joint of human neck-and most of vertebrates- is Atlantoaxial. Not a ball-and-socket joint like your shoulders. Meaning it has a limited turning radius. Therefore it cannot twist 360°. I don't understand what are you scared of. 

◇"B-But if you reverse the song-" a shit ton of vocaloid AND NON-VOCALOID songs have hidden messages in their reverse. It's nothing new nor terrifying.

◇Second of all, even the instrumental isn't scary. It's just a synth, drums, and some laughter for a few seconds. In fact the beat is fucking fire. 

◆The girl, isn't in fact scared by her mom's twisting neck, BUT because her mom is coming.

◆She definitely doesn't have a good relationship with her mother. In fact the mother is probably abusing her.

◆Maybe the "twisting neck" is a metaphor of looking for something to spank her child for.

◣THIS SONG IS A DARK SONG BUT it's not the only song on the topic of child abuse, and definitely isn't more disturbing than the other ones. I can name a million. Let's name kikuo's "you're a useless child" for example. ◥

What I'm assuming is frightening to the audience is the visuals. The cover art Showing miku without light in her eyes -traumatized or dead- and the dark theme and lyrics being written on the screen in red. 

Overall, don't be afraid. Your sleep paralysis demon won't kill you after listening to this song.