What is Ka-mon
Ka-mon (家紋) are Japanese emblems used to decorate and identify an individual or family. While Mon is an encompassing term that may refer to any such device, ka-mon and mondokoro refer specifically to emblems used to identify a family. An authoritative mon reference compiles Japan's 241 general categories of mon based on structural resemblance (a single mon may belong to multiple categories), with 5116 distinct individual mon (it is however well acknowledged that there exist lost or obscure mon that are not in this compilation).
The devices are similar to the badges and coats of arms in European heraldic tradition, which likewise are used to identify individuals and families. Mon are often referred to as crests in Western literature; another European heraldic device similar to the mon in function.
Mon may have originated as fabric patterns to be used on clothes in order to distinguish individuals or signify membership in a specific clan or organization. By the twelfth century, sources give a clear indication that heraldry had been implemented as a distinguishing feature, especially for use in battle. It is seen on flags, tents, and equipment.
Like European heraldry, mon were initially held only by aristocratic families, and were gradually adapted by commoners. On the battlefield, mon served as army standards, even though this usage was not universal and uniquely designed army standards were just as common as mon-based standards. (cf. sashimono, uma-jirushi) Mon were also adapted by various organizations, such as merchant and artisan guilds, temples and shrines, theater troupes and even criminal gangs. In an illiterate society, they served as useful symbols for recognition.
Japanese traditional formal attire generally displays the mon of the wearer. Commoners without mon often used those of their patron or the organization they belonged to. In cases when none of those were available, they sometimes used one of the few mon which were seen as "vulgar", or invented or adapted whatever mon they wished, passing it on to their descendants. It was not uncommon for shops, and therefore shop-owners, to develop mon to identify themselves.
Rules regulating the choice and use of mon were somewhat limited, though the selection of mon was generally determined by social customs. It was considered improper to use a mon that was known to be held by someone else, and offensive to use a mon that was held by someone of a high rank. When mon came into conflict, the lower-ranked person sometimes changed their mon to avoid offending their superior. The mon held by the ruling clans of Japan, such as Tokugawa's hollyhock mon and the Emperor's chrysanthemum mon, were legally protected from unauthorized usage.
Occasionally, patron clans granted the use of their mon to their retainers as a reward. Similar to the granting of the patron's surnames, this was considered a very high honor. Alternatively, the patron clan may have added elements of its mon to that of its retainer, or choose a completely different mon for them.