Dragon paintings are nothing new, but creating them with a single brush stroke is definitely something you don't see everyday. These paintings are known as Hitofude Ryuu (dragon with one stroke) in Japan, and the ones you're about to see are from a studio called Kousyuuya in Nikko, Japan. Continue reading for two more videos and information.
According to This is Colossal, "The process involves carefully painting an ornate dragon head with various flourishes, and then finishing the piece using a giant sumi brush in a carefully orchestrated stroke. The process has much in common with both ink wash painting and calligraphy, and similar to letter forms, the images are often repeated. From the videos you can see certain designs are reused in different colors or with added details. All the videos here start at the fun part where the torso is painted, but you can rewind them a bit to see the creation of the entire painting."
[Sources 1 | 2]