Instructions
Preparation
Make sure you play through Hanzo's story mode at least once.
Recruit a partner. You will need one for this.
Make sure Hanzo is ready for battle. Give him the power bracer and attack bonus skills.
Reset if you have to. Lower level players make for easier enemies.
Get a good 4th weapon with at least 2 bonuses at +20 or better.
The Battle
Start the Battle of Mikatagahara on Hard difficulty. Yes, you can do it on Chaos, but do you enjoy punishing yourself?
Defeat Nobushige Oyamada in the northwest and then protect your general from the Takeda.
Keep your generals alive and prevent the Crane Formation from collapsing. This is critical!
Have your buddy run around whacking all the generals except Shingen Takeda.
Watch for the officer that attacks Kazumasa Takigawa and eliminate him when he shows up. He is the biggest reason the Crane Formation crumbles.
Take the western pass and use the ninja path.
Close all the gates when you are prompted to do so.
Eliminate the Supply Unit that appears in the southeast corner for the weapon. They move west and always toward the closest gate.
Finish the stage and enjoy your Yamikiba!