Both are epic movies about epic wars that determine the fate of the country during warring States of both countries. In Both movies, a noble lady of a warlord psychologically stalls, defeats opponent/rival warlord using simple tea ceremony. Both movies are about two of greatest East Asian ambitious brave wise virtuous military generals, strategists.
Both are epic jidaigeki Samurai movies about epic Fiercesome battles of warring States period, two of greatest Military campaign led by Ishida Mitsunari, on behalf of his Lord, Hideyoshi. Both feature conquests, exploits of Ishida Mitsunari, great brave, loyal, highly ambitious, wise strategist, war general of Hideyoshi, second great warlord to unite entire land of Japan. Sekigahara is more-or-less like sequel of a kind to Floating Castle.
Both are epic jidaigeki movies about betrayals, Rebellion committed by inferior warlords, towards, faced by two of Japanese great warlords with grand ambition of unifying entire land of Japan, perishing one after another in quick succession, two major events of betrayals in succession, that drastically changed, altered the course of Japanese history entirely.....................