As soon as you begin the demo take the first staircase to your right and walk up.

At the second store/shop on your left (it is a resturant/food court) enter the shop and jump behind the counter and walk to the juice section (you'll see it, mmmmm O.J.) after you replentish your health,walk to the right of the juice section and jump off-trust me.

You will land on an orange canopy and yeehaw you'll find the Katana that will slice and dice the hoards of zombies in your path. All though the katana does not last long, it is freakin sweet watching the zombies be cut into bloody pieces!

Note katanas are also infinite from stalls N116 and E205.