>>14758526
A sequel set during the bakumatsu period would be neat, though I feel like the only option for a protag in that setting would be Yoshida Shouin.
Nanbokucho could work, or you could really turn the clock back and set it during the mongol invasions.
I personally would love to see a game in the vain of Nioh set in antediluvian times. Just imagine being an atlantean warrior invading the mediterranean, and the return to Atlantis after Lucifer ressurects the evil spirits who posses the world's elite.