In the month of May you may have seen a lot of streamers with the koi or japanese carp symbol flying around Little Tokyo.  The banners were for Children's day (formerly Boys day) which is on May 5 every year. The koi is supposed to represent strength and perseverance and is s common motif seen in not only Japanese but Chinese culture too.  The main legend is that a group of koi were swimming upstream towards a waterfall.  Once they reached the end of the river at waterfall many koi became disheartened and turned back.  A group of gold koi began to try and jump to the top of the waterfall each time failing, but they kept trying.  Watching from the river bank was group of demons who mocked the unsuccessful koi and even made the waterfall higher out of spite.  After hundreds of years of trying one finally made it.  The gods were so impressed with the koi's perseverance and determination that they turned the gold koi into a dragon.

The koi symbol is a popular among the warrior class and martial arts as the symbol to never give up regardless of the odds.  The koi are often depicted swimming up a waterfall, with men or boys riding them or two koi swimming in a circle.