Mushi: the most basic forms of life in the world. They exist without any goals or purposes aside from simply being. They are beyond the shackles of the words good and evil. Mushi can exist in countless forms and are capable of mimicking things from the natural world such as plants, diseases, and even phenomena like rainbows. This is, however, just a vague definition of these entities that inhabit the vibrant world of Mushishi, as to even call them a form of life would be an oversimplification. Detailed information on Mushi is scarce because the majority of humans are unaware of their existence. So what are Mushi and why do they exist? This is the question that a Mushishi, Ginko, ponders constantly. Mushishi are those who research Mushi in hopes of understanding their place in the world's hierarchy of life. Ginko chases rumors of occurrences that could be tied to Mushi, all for the sake of finding an answer. It could, after all, lead to the meaning of life itself.

Ghostly, primordial beings known as Mushi continue to cause mysterious changes in the lives of humans. The travelling Mushishi, Ginko, persists in trying to set right the strange and unsettling situations he encounters. Time loops, living shadows, and telepathy are among the overt effects of interference from Mushi, but more subtle symptoms that take years to be noticed also rouse Ginko's concern as he passes from village to village. Through circumstance, Ginko has become an arbiter, determining which Mushi are blessings and which are curses. But the lines that he seeks to draw are subjective. Some of his patients would rather exercise their new powers until they are utterly consumed by them; others desperately strive to rid themselves of afflictions which are in fact protecting their lives from devastation. Those who cross paths with Mushi must learn to accept seemingly impossible consequences for their actions, and heal wounds they did not know they had. Otherwise, they risk meeting with fates beyond their comprehension.

During the Edo Period, 3 mysterious space capsules were sent down to earth. Fear that it might bring chaos to the earth, the humans at that time buried these 3 objects down beneath the ground and entrusted a piece of descriptive map to the Kamui family. Today, these 3 objects were awaken one by one. The first to awaken, Tri-Zenon, one of the Zenon Guardians is now driven by the descendant of the Kamui family, Akira Kamui, his brother Ai Kamui and his friend Kanna. Aliens who descend to earth with a purpose will now have to face Tri-Zenon.

There once existed a planet named Beal, until it was wiped out by the mysterious entity known as Gaizok. The few remaining survivors escaped to Earth and split into three families, named Jin, Kamie, and Kamikita respectively. While attempting to start a new life, the collectively known Jin Family prepared for the inevitable Gaizok invasion on Earth and its giant mechanical beasts known as Mecha Boosts. In order to defend their new home, they have built three vehicles which when combined form the mighty Zambot 3. The Jin Family must not only defend against Gaizok attacks, but also harsh criticisms from the very people they protect, who blame the Jin Family for the invasion in the first place. (Source: AniDB)