Industrial Highway 357
Run along this stage fighting the enemies, shortly after the second boat goes past on the left, there will be an Alien hiding behind some containers to the right. There will also be an armed enemy here, so make sure to take him out quickly. You’ll soon be jumped by a big group of enemies.
Soon you’ll reach five crates in a line to your right. In one of these is a weapon, which makes it much easier to deal with the swarms of enemies. You’ll reach another set of four boxes soon and you’ll face Hwoarang. Defeat him to unlock it.