It takes place in a post-apocalyptic Tokyo,

A disaster that happened a long time ago.

In the past, there was an oppressively passionate hero who saved over a thousand people by himself

Since ordinary humans can't see it, they'll think the destruction was caused by an earthquake, tornado, or other disaster.

Natural disasters, big accidents, and selfish villains.

Just about eighty years ago, there was a terrible disaster. The cliffs overlooking the Sea of Ghosts collapsed, taking most of Winterhold with them.