Disastrous New Age

Disastrous New Age,

10 years ago world was attacked by monsters that appeared from portals.
Countries used all of their nuclear weapons to kill them.
Radiation spread over the whole world while a lot of people died.
Then a message appeared before every person.
[Congratulations for clearing the Tutorial Stage.
Reward: Clear all radiation caused by nuclear weapons.]

Lucian is living in a house that barely stands. He often got beat up by others because he was so weak when he was young.
So? Will Lucian stay weak all of his life or will he become strong and rise to the top in this world where only the strong can survive.