Kannon is a Kannon who rides a dragon among the clouds. 
Kannon and dragons are closely related, and Kannon is one of the 33 Kannon.

Kannon is the one who punishes the Dragon King who brings floods, while the gentle dragon always obeys Kannon.
It is said that the Dragon King calls the clouds, brings rain, and grants a good harvest, so while praying to the Dragon King, people also pray to Kannon to stop the Dragon King from becoming violent.

The dragon is a water god, and Kannon came to be depicted standing on the head of a dragon.