菊花紋章 (kikka monshou), 菊紋 (kikumon), 菊花紋 (kikka-mon) or 菊の御紋 (kiku no gomon)
A stylized depiction of a 16 petal chrysanthemum flower, used by the Emperor of Japan and the Imperial Family. It is most notably seen on the bows of warships of the Imperial Japanese Navy and on the covers of Japanese passports. Be careful not to confuse it with the 5 petal sakuramon.
For clear examples, check the obi's of Akiha (post #15614) and Megurine Luka (post #568974), and the bottom-right side of Yuyuko's kimono (post #570756).
