Sanada Yukimura (1567-1615) is one of the most popular samurai of all time.
The design of the Sanada family crest is called "Rokumonsen" (6 coins). This name was derived from teachings of Buddhism, "Rikudo." "Rikudo" means six underworlds, which people would go down to after death. When one died, the bereaved gave "Rokumonsen" into the casket, which was believed to be needed to cross Death's river.
Sanada took this concept into the family crest, and this was a message that they were not afraid of death and ready to die anytime in the battle.
The banner and crest with Rokumonsen and Sanada's signature color, blazing scarlet must have terrified their enemies.