Found this a few days ago and enjoyed immensely the 100 odd translated web novel chapters. It is a mixture of elements from Pacific Rim, Gate, Grimgar, fantasy and apocalypse.
One day, for no reason, monsters start to appear in the world. Whomever kill monsters, can gain experience, jobs and skills. Electricity, internet, phones, civilisation as we know it is gone. The world is overwhelmed in matter of hours by randomly spawning monsters. The story revolves around Kazuto and his struggle to survive using his wits. From time to time, we get POV of other survivors, but most of them has a very short life expectancy.
I never felt bored while reading it, writer knows how to build suspense and keep the character on their toes. The side characters has enough depth to them to make you as a reader, root for their survival. However, the story is very cruel and gives off the feeling like you are witnessing the last days of mankind as they get eaten, mutilated and destroyed by monsters.
There is 100 odd translated web novel chapters, go read it yourself. Kazuto abusing Item Box for all its worth by squashing monsters with heavy machinery never gets old.
Spoilers for why monsters has appeared
spoiler
