Eye B.

The literal portal to the Watchful World, EYE (not real name) used to be a simple human boy. 

By making shapes with his hands and body, he can create portals to the Watchful World

Summarized backstory: Abandoned as a child, Eye was chosen by the Watchful World to become their portal. Whether you would define it as a curse or a blessing is up to ones own tastes but he became a catalyst for them. At the beginning, the child was dragged into the WW for a short period of time to recover and he came out- different. He came out healthy, definitely in better shape than previously seen, but there was something changed. What remained was the very reason why he was dragged into the WW to become their representative- a strong passion to know the unknown. To watch all events happen.

It would not be odd to say "This kid seems to be everywhere!" as his literal job is to watch all humane and monster events play out. Whether there are other Watchful World representatives is unknown.