Double Circulation refers to the movement of chakra to make ki, The main area of ki generation is in the abdomen, however recently, new information has come to light about a technique developed by a man named Shigenosuke. He believed that yin/yang circulation in the body should not be thought of as circular, but as a two body rotation. The Mark of the Battling Gods he created artificially alters the bearers’ ki generation, and in turn, their entire body. Rather than recreate it, Ryoga learned the secret of how it worked.
He discovered that the Mark isn’t needed to alter the flow of chakra to produce ki. That same potential can be unlocked by good old fashioned training. This technique circulates user’s yin and yang slowly around the Manipura, using orbits rather than a single coiled circle.
From a step by step process the movement of chakra is like the wheel of a pump or piston. The interaction of yin and yang produces ki. The emptiness of the mind, produced by a state of , allows the ki to externalize: it leaves the body, and there, it is made subject to conscious thought. When you circulate this fast, the aura pulses incredibly quickly. The technique is better for straight up ki techniques, like the Shishi Hokoudan. It causes some stability loss, but produces a lot of power. Problem is, you still get some interference from the chakra points above and below. The faster you go, the wider it gets. It was a bit like easing into cold water instead of just plunging in.