name the unique name of the flag of japan
Kikkamon
Flag of Japan

The current Emperor's flag is a 16-petal chrysanthemum (called Kikkamon , Japanese:菊花紋) , 
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Flag of Japan [SEP] Imperial flags
The chrysanthemum has been associated with the Imperial throne since the rule of Emperor Go-Toba in the 12th century, but it did not become the exclusive symbol of the Imperial throne until 1868.