As you know koi fish is thought to be a symbol of success in Japan.
An ancient tale says there is a vigorous upstream somewhere on the Yellow River. The waterfall at the end of the upstream is called the Ryumon-Gate (literal translation is Dragon Gate).
Many koi gather around the basin of the Ryumon-Gate. If a koi swims the waterfall up it’ll become a dragon and fly away.
Bakegoi (Dragon fish)
The koi gets spiky in progress.
Single/double horns grow and the fins get bigger.
The fins turn into wings.
Ou-ryu (Hiryu)
Legs grow.
It’s called Ouryu in this phase.
The tail gets longer.
Finally it swam the waterfall up and turned into a dragon.
Tebori Tattooist Ryugen
Roppongi Tokyo