The story takes place in the interstellar universe, where everyone born with a tag on them(S, A, B, C,) which created by the Godlike Emperor who rules 3/4 of the universe from Millenniums. The Tags gives the higher tags complete domain over those tags, this age knows as Dark Age.
The tale is about a young boy named Atlas, who woke up on an unknown planet and found everyone on the planet dead. He is a boy born without a tag on him known as "untagged".
The untagged is the individual how possed the strength or talent to rival the Emperor and conceded as the symbol of terror and destruction.
The story starts when the boy escapes from a slave dealer to find his mother and thus the tale of an Untagged boy, who brings an end to the Dark Age begging.