Apocalypse with game-world setting

#1
I forgot the title of this good story I had read more than one year ago, the characteristics that i remember are:

-mc was a loner or a really ordinary boy in class before apocalypse
-the apocalypse happened when mc was on the school, but for some reason he was situated out of the classroom, when he got back everyone already scattered (?)
-he met a goblin and later a goblin king on his way to the class, got lucky to kill it, and because he is the first 'participant' who got a kill point, he earned a title "A Pioneer" or something
-met a girl who is a classmate and hid together in some classroom, later the girl got power in the form of a floating ball of light
-when apocalypse started the world become a game system where there are status window, skill, etc.
-the fic is quite famous one year ago(?) i remember it getting posted on the board (?)

Thanks a lot! ??

~aFallenLeaf??
It's not the time for an adventure anymore..

Let's sip on some warm tea while watching leaves falling from the trees?~??