I Become Invincible after She Saves Me

In 2514 of the New Era, the apocalypse came. A world-class phenomenon appeared. Many strong mutated beasts have been wandering around the world since then. Humans are under deadly threats. They can only struggle for life. The one who will save everybody and protect the world from collapsing is... an average-looking barber from the slum? (Source: Webnovel)