The user breathes fire along a cord or any other type of long object, which rushes forward in a straight line catching the enemy on fire. A line of enemies can be used as the conductor as well. The flames are meant to target, and assault the enemy's upper body. While in the manga, the technique is shown to be just a small burst of flame running along a line of wire, the anime shows it to be even larger and more devastating than the Fire Release: Great Fireball Technique, able to melt through a person's skin, and even rock.
"Ryūka" (流下) can also be translated as "downward flow", which fits the nature of this technique.
In the anime and OVA, this technique has been used without a conductor, but the enemy was much closer in both cases.
In the second OVA, this technique begins like the anime version of this technique but the blaze splits into multiple smaller dragons of fire that strike the foe from multiple directions.