Keiji's real name historically is Toshimasu ironically. The name Keiji comes from Edo legends, which mean "lead cautiously" due to his reckless personality. A lot of Keiji's visual design is inspired by his characters in the comic Hana no Keiji. His line during his Musou "Why do you think tigers are strong? Because they were born that way!" is a quote from the comic. His alternate outfit is also a reference to an event in the comic where Keiji shaves his head as a peace messenger to Ieyasu.

Many of Keij's weapons and fighting style are also inspired by kabukimono as he celebrates and dances during battle.
Contributed by DrakeVagabond
The initial idea for Hideyoshi's design was based on Nobunaga's real life nickname for him, Monkey. Much of his design was inspired by Sun Wukong from Journey to the West, and his weapon was made to mimic the swings and curls of a monkey's tail.
Contributed by DrakeVagabond
Kunoichi is inspired by the Sanada Ten Brave, a legendary group of ten ninjas created by Yukimura Sanada to serve under him. Kunoichi was likely created as a representative for the legendary group overall. However, members of the group do appear in the game as body guards.
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Lu Bu from Dynasty Warriors can be made playable by hacking the game. It is also possible for Lu Bu to randomly appear as an enemy in place of Keiji Maeda or Tadakatsu Honda on level 30 of Survival Mode on Abyss Difficulty.
Contributed by DrakeVagabond
Initially, the designers aimed to portray a Nobunaga that didn't look too similar to his designs in the Nobunaga's Ambition series.
Contributed by DrakeVagabond