Warriors Orochi - Wu Chapter 6-X - Battle of Osaka Bay | Unlock Keiji Maeda

Keiji is one of the hardest to unlock as you have to keep all your allies alive, get all your reinforcements, and get them all to reach Keiji within 20 minutes. I did this at like 19 minutes into the stage. Playing on Easy will make it go faster, as well as a fast horse so you can just drive-by all the enemies and hit the drum fast. Get them all to him in time, then beat him, then you get him.