Just because this boy was granted the weakest sword doesn't mean he can go back on his promise with his childhood friend in this fantasy manga!When everyone turns 12 years old, they are granted a Mystic Arms by God. The hero-admiring Rust dreams that he'll get a powerful one of his own one day. As his fellow villagers began receiving high rank Mystic Arms one after another, Rust nervously prayed to God. Then, before him appeared a Mystic Arms of the lowest rank, a Rusty Sword. A tale of becoming "zeros to heroes" with the weakest boy and the lowliest weapon!