There are about 200 types of dragonfly in Japan, each with its own name, and I have absolutely no idea which ones these photos are of, so I use the generic "Tombo"
Associated with late summer and early autumn, the Tombo has a deep and rich relationship with Japanese culture, not least of which is an ancient name for Japan meaning Dragonfly Isles.
Found as an artistic symbol as far back as the Yayoi Period, the dragonfly was adopted by samurai and appear on helmets and swords. It also appears much in Haiku.
With the heavy use of chemical pesticides the tombo no longer appear in the numbers they used to.