This film is set at the beginning of the Warring States era of Japanese history, which most Japanese film viewers would have studied extensively in school. Unfortunately for Western viewers, these historical aspects are therefore given little exposition, making some aspects of the film hard to follow for those without such schooling.
Here are some attempts at "liner notes" to help in understanding and appreciating the film (warning: I'm not Japanese and have not had Japanese schooling):
* Shingen Takeda is a warlord vying for power with Oda Nobunaga and his ally Ieyasu.
* Takeda had a reputation for the military prowess of their cavalry. Thus, you see lots and lots of horses featured in the film. Horses were important to the clan. Takeda's symbol is the four diamonds (the exact symbolism is explained in the film). Just as in the West, use of such heraldic symbols in war banners and clothing was very useful in figuring out who is who. So, keep in mind that when you see the four diamonds, whatever their color, those are Takeda forces.
* Nobunaga was known for his adoption of many Western ways. This is why he wears European-influenced clothing and doesn't have the standard samurai haircut (basically, shaved head, topknot). Nobunaga was also known for his use of rifles in battles. So, one of the themes of the film is the struggle of tradition against the influence of the West (in the film, mostly shown through the use of guns although their is also a brief shot of some clerics). Nobunaga's symbol is the five-sectioned flower. Nobunaga is also known for his love of Noh dramas, a dramatic form incorporating difficult-to-understand archaic language and restrained, careful action, somewhat like the film "Kagemusha" itself. Nobunaga launches into a bit of Noh at one point in the film.
* At this early time, Ieyasu was mostly known for his political survival skills. Ieyasu is probably best known to American viewers as the basis for James Clavell's Toranaga character in "Shogun". (Nobunaga is also in "Shogun" albeit as a minor character and under a different name.) The events in this film take place roughly two decades prior to those in "Shogun".
* Takeda's generals each also have their own symbols to help you track them. One of Ieyasu's generals also has a "symbol" (actually, the character "hon", which IMDb will not display).
* Haircuts are a sign of rank. This is why all the lords (except Nobunaga) have a certain haircut, all the pages have the same hairstyle, and so forth. The haircut~rank connection figures even more strongly and explicitly in Kurosawa's "Throne of Blood".
* Japanese men during this period often changed their names as their status changed. For example, in "Toshie to Matsu", Toshie, who is one of Nobunaga's (and, later, Hideyoshi's and Ieyasu's) generals/lords is granted the honor of changing his name to one which incorporates part of his lord's name into his own. Keep this in mind as Takeda's son discusses the use of his father's name and symbol.
* Miltary success and bravery in battle were key means of advancement. Thus, military leaders of this time are often depicted as ever-volunteering to do brave (even stupidly brave) things in hopes of gaining greater status. In "Kagemusha", Takeda's son is desperate for such advancement.
