People are in Star Iron, and the game begins with the unsheathing of Heavenly Fire.

Ron, as the chief scientist of the Firemoth, found himself awake in the Black Tower Space Station after defeating the Herrscher of the End in the pre-Honkai era.
Then, to his surprise, he discovered that the Heavenly Judgment he had used in the previous civilization had also appeared beside him—
In short, this is the story of a genius scientist who wields the Judgment of Heavenly Fire, causing numerous disasters to befall the Star Iron World.
"I will defeat all enemies, even if it costs me the Black Tower's life!"
"Skyfire! Unsheath!"