There comes a point late in the game where you’re inserted into the Nibel Plains and are given a rifle to take out enemies from afar. There’s a level-up system on the rifle that’s explained before you kill the first enemy. While it seems that you can’t possibly level up the rifle entirely before you reach the conclusion of Nibel Plains, you can actually backtrack at certain points to make enemies respawn. By doing so, you can accumulate seemingly-endless amounts of experience to be used on your rifle.