Since they're already advertising, it's clear that everything said in the advertisement is true; the Holy Grail people really do treat Metropolis as their playground.
They Delete their memories, lower their thresholds, and experience the loves and hates, the joys and sorrows of the lower classes within Metropolis.
Beyond filming a reality TV show, Metropolis serves another purpose for the Holy Grail people.
To tell the truth, Sun Jack wasn't surprised at all by this situation.
This was just a new form of exploitation. Sun Jack believed that Metropolis must hold other values for the Holy Grail.
Though he wasn't surprised, Sun Jack knew he had to react now.
"No! This can't be happening! I'm a Holy Grail Person? I... I came down from the Holy Grail to play? I've been rebelling against myself all this time?" Sun Jack cried out in disbelief,