My Best Friend Is Devouring This World

Help! I think my childhood friend has turned into Ultraman!

He goes to work right on schedule every day, fights monsters, saves the world, and looks incredibly cool!

But something seems a little off...

Dude, why are you eating the monsters and taking leftovers after you beat them?!

The whole world thinks it's just his unique way of replenishing his energy. I'm the only one who knows he's sliding into madness.

Until I discovered where those monsters came from... They were missing people!

I'm doomed. How do I tell the world that their hero is actually an ultimate devil who feeds on people?

Waiting for an answer. This is urgent!