The term “kamon”, or simply mon, refers to a crest used in Japan to indicate one's family lineage. Kamon are often referred to as “Family Crests”, but they are different from European coats of arms in many ways.
The origin of kamon goes far back to the latter part of Heian Period. Around that time nobles began placing their own mon on oxcarts to move around the streets. Afterward, when the conflict between Heiji-clan and Genji-clan became more violent, mon became popular among warriors too and new designs were created. Samurai, in fact, used their original symbols on flags and tends to advertise their achievements or to show off and by the middle of Kamakura period, this was an established custom among samurai class. Kamon spread widely and was used on even graves, furniture, lacquerware and of course helmets and armor. Differently, from Europe, where heraldry follows strict rules for design and colors depending on bloodlines and status, in Japan, there were no limitations in choosing a symbol. This free use of other family's kamon caused frictions between clans and for this reason, there was an unspoken rule to avoid using a kamon already in use by high-class families.
During the peaceful Edo Period, kamon became a sort of decoration that would state the owner’s status. Japan was, in fact, a hierarchical society of samurai, farmers, artisans, and merchants and mon were used by all of them, as an indication of one’s rank. This is probably the biggest difference to European heraldry, where only aristocrats could use a crest: farmers, tradesmen, craftsmen, and even actors and prostitutes used their own kamon as a personal mark, in the same way, contemporary companies use a logo to be immediately recognized.