There are various opinions as to the reason that Mon were created in Japan. Strangely, both main reasons are largely parallel with the set-up of the European system of heraldry but with a different visual outcome. The predominant reason is that noble families started to use them at the end of the Heian Period (794 - 1185) when Japan was governed by the nobility - primarily the Emperor. Noble families attached Mon to their belongings as identifying symbols and tried to make their own beautiful decoration look appealing. That is why a lot of Mon use designs that include flowers and plants, etc.
After the Kamakura Period (1185-1333) when Japan was ruled by the Shogun - which was the military commander with the highest authority among the samurai - most of the warlords across Japan started to have their own Mon. Compared to the graceful design of the nobility's Mon, those of the samurai clans were designed as practical symbols to be put on flags, helmets and armour so that they could be seen at a glance in battle. As the purpose of the Mon for samurai clans was identification on the battlefield, simple geometric designs were devised that allowed them to tell the difference between one clan and another at a glance.
The Chrysanthemum, or Kiku in Japanese, is a symbol that represents longevity and rejuvenation. When first introduced to Japan during the Nara period (710 – 793), the Japanese Imperial Family was fascinated with the Chrysanthemum. Eventually, during the passing of the years, the Chrysanthemum become the Imperial Family Mon. As you will see from the representation of the Emperor's Standard above, the Imperial Seal of Japan features 16 petals at the front and 16 petals at the back (where only the tips of the petals are visible). There are other Chrysanthemum seals or Mon with different numbers of petals, usually related to other branches of the Imperial Family, as we will see. Nowadays, the Japanese Diet (Government) uses the plain 16 petals seal for official documents (passports, orders, etc).
The Emperor's Throne is referred to as the Chrysanthemum Throne and carries the emblem on chair back. The highest order of chivalry in Japan is the Supreme Order of the Chrysanthemum, awarded by the Emperor.
Having said that, some speculate that the Mon represents the sun. In Japanese mythology, the first Emperor, Jimmu, was a descendant of the sun goddess Amaterasu.
Whatever the origin, a decree was issued in 1871 at the time of the Meiji Restoration and the establishment of modern Japan, that forbade the use of any Mon which could be mistaken for the Emperor's. It also specified that the Emperor's Mon had a small disc in the middle to signify that his, alone, was viewed from the front. Imperial princes not only had a Chrysanthemum Mon with 14 Petals but also showed the calyx of the flower to signify that it was viewed from below.
The following Mon are for various princely branches of the Imperial Family. If anybody has any specific information regarding the extra elements, the equivalent to cadency in the western world, and any history behind them, I would be extremely grateful.
As such, his branch of the Imperial Family was granted its own Mon, still retaining the Imperial Chrysanthemum at the centre with 14 petals at the front and 14 at the back. The ruling with regard to the calyx seems largely to be ignored nowadays.
Again, he was authorised to start a new branch of the Imperial Family in celebration of his wedding to Hanako Tsugaru, who is now Hanako, Princess Hitachi, and was granted the above Mon which similarly shows the Chrysanthemum with 2 times 14 petals.
Prince Hitachi is mainly known for philanthropic activities and his research on the causes of cancer.
He was a career soldier and was shocked at the army's conduct in China during World War II to the point of advising his Brother to abdicate and take responsibility. The Prince later turned to studies, mainly about the Middle East.
Although Prince Misaka died only a couple of months short of his 101st birthday, his wife, Yuriko Takagi, daughter of Viscount or kazoku Masanari Takagi, survives him as the oldest member of the Imperial Family. His eldest son, Prince Tomohito of Mikasa, was naturally expected to inherit the full title of Prince Misaka but Tomohito, nicknamed the Bearded Prince, died of cancer before his Father, aged only 66.
The Mon of the Misaka branch also contains the 14 double-petalled Chrysanthemum.
Yoshihito was, in fact, the last remaining male descendant of Prince Mikasa. He never married nor had any legitimate children and so his death marked the end of his Father's branch of the Imperial Family and also his own branch.
Yoshihito, Prince Katsura's Mon shows the 14 double-petalled Chrysanthemum within a rather geometric framework patter rather than surrounded by plants or flowers.
He received the title Prince Takamado and authorization to start a new branch of the Imperial Family on 1 December 1984 in celebration of his wedding to Hisako Tottori, eldest daughter of Shigejirō Tottori, which took place 5 days later.
His early death, following a game of squash, shocked the nation. He and his wife, Hisako, Princess Takamado, became known as the most widely travelled of the Imperial Family; a tradition which Princess Takamado has maintained. Their three daughters are excluded from inheriting the Takamado title.