Amazon Delivery Samurai School

After a violent explosion in a scientific faculty in Armenia releases unexplainable amounts of energy, an interdimensional portal opens a path for horrors beyond human comprehension. The area from Ukraine up to China is radioactively contaminated, German scientists attempt to find the source of the portal's energy and close the portal, people in the contaminated area try to survive, but there's something more - amazon delivery. Even after the radiation has spread around the globe, people couldn't bid adieu with deliveries. This caused amazon and aliexpress to start professional warrior schools that trained fierce combatant couriers who would use melee weaponry to quickly deal with mutants and bandits on their way to the delivery target. Even though they travel only on foot, they're lightweight enough to run swiftly and graciously as the fly of a swallow. China, being a mass manufacturer mostly unaffected by the radiation and land connected to Europe, has become the place where these delivery schools become based - but there's something more to this story...