Like actual guns, Nug!!, er, I mean, Upotte!! should be handled with caution.
Japan has been known for pulling off some unusual stunts in their media and markets as a whole. A good bunch have been incredibly successful, while others... not so much. Upotte!!, on the other hand, takes the cake in this world of unusual things, not because of its premise, but its execution.
So the premise can easily be summed up in ten words: "Upotte!! is a slice of life ...