And handed down in writing. Carp flag, taken from the meaning of China's "Book of the Later Han" carp leap Dragon Gate story. Ancient legend has it that the carp in the Yellow River will change into a dragon when it jumps over the Dragon Gate.

Some other stories also cite this story, often using "carp jumped the dragon door" to compare to the success of the examination, promotion, and so on, to become successful.

Li Bai, the poet, also wrote a poem about this: "Three feet of carp in the Yellow River, which resides in Mengjin, does not become a dragon, and comes back to accompany the ordinary fish". From the historical records can be seen, koi flag is the cultural heritage of our country, also began in our country. It is not Japanese, not to mention belonging to Japan exclusively.