Remember back in 2013 when Kpop went into full supernatural concept mode?
From EXO's Wolf, VIXX's On & On, Boyfriend's Bounce, etc, etc... there were vampires, aliens, werewolves galore.
Nowadays in 2016, though, we're seeing a rise to realism. BTS dealing with drugs (I Need U) or Monsta X dealing with totalitarianism (All In)
"Zombies are the perfect metaphor."
Basically, using the supernatural has always been a way of talking about real life issues, without actually bringing them up.
For example, in Harry Potter House Elves would represent slaves, the discrimination and fear of werewolves represented how ridiculous racism is, etc. Fiction allows us to talk about important issues in a sly way.
For example, VIXX's Hyde portrayed them as vampire-like, living in a spooky house and dark forest, growing black wings and almost being taken over by a monster.
At its core, this is a song about dangerous relationships. A partner who is emotionally unstable, but charming. Hurting you but begging to have you back. This can be a metaphor for abusive relationships of all kinds.
They repeat over and over that "that man isn't me, there is a crazy 'other me' inside of me." Just as abusers usually do after a moment of violent anger.
Hiding this message behind the mask of "monsters" and "dark angels" makes it easier to consume and talk about. But take away the supernatural and its a serious issue they bring up.
Another great example is Monster by Big Bang.
They dress up as literal monsters, but talk about how just because they are different and not fitting into the society's mold they aren't bad people.
It's an anthem for misfits, and a message to society to stop being so cruel.
So why are we shedding the costumes now?
Why are things suddenly more...real?
We're done hiding.
The problems can no longer stay hidden, we need to talk about them. No more using vampires and ghosts as metaphors, the general public is more comfortable discussing issues like depression, drugs, mental health, discrimination, etc.
The move to realism means that we're being realistic about the problems - we're addressing them head on.
That being said, there is nothing wrong with supernatural concepts being used to talk about issues!
Often people can't understand something in its original form. For example, maybe someone doesn't see the need for LGBTQ+ rights. Give them a love story with a couple that is forced apart, never to be together (perhaps a vampire and a human??) because society says its unnatural.
If while reading the story or watching the movie, that person feels upset about this poor couple torn apart by society, maybe they will see the correlation between their belief that gay marriage is wrong.