It seems like I can remember a good portion of the story but not the actual name of it so I'm going to try describing the story and the first chapter since that it what I seem to remember best.
It starts off telling you how there are creatures in the world that hunt humans. To combat these creatures certain humans gain the ability to use special weapons unique to each individual. At the begin of the story there is a team of people considered to be the strongest of these hunters. One of them has a younger brother that likes to sneak out of the village and watch his brother and his friends train because he to dreams of becoming a great hunter and putting an end to these creatures forever. One day when sneaking out of the village to watch his brother train one of the most powerful creatures in the world attacks and almost kills the boy. To save him the brother and his friends sacrifice themselves transferring all their abilities to him. A few years passes and you find out the boy has been gone for the past few years hunting and training and it due to return to the town that day. I can't remember why exactly but it ends up with the boy destroying a very powerful creature that attacks all though it appears the boy should still be weak. He then ends up having someone look into his eyes that's supposed to "level him up" and finds out he is actually really powerful he just hasn't been "leveling up"? Shortly after that the boy leaves with a childhood friend and later meets up with another guy and they go to hunt these creatures.
I also seem to remember that the main character only sleeps once every several days only to immediately pass out and not wake up for 24 hours or something like that. I also seem to remember that it has a sequel. The weapons the boy uses include a gun, shield, spear, and I think a couple others but those are the ones I remember best.
Hope that enough information for somebody to remember it because I've search for it several times and have never been able to find it again. Thanks for the help!