According to traditional Tsurukokan philosophy, the entirety of nature is composed of five elements, collectively known as gogyō: wood (ki 木), fire (hi 火), earth (tsuchi 土), metal (kane 金), and water (mizu 水). Every creature and object, animate or inanimate, is composed of one or more of these elements to varying degrees.
In nature, each element produces or controls another. This is known as “generating” and “overcoming.” In the generating cycle, each element produces another: wood feeds fire, fire replenishes earth, earth generates metal, metal invigorates water, and water nourishes wood. In the overcoming cycle, each element controls or diminishes another: wood breaks up earth, earth dams water, water extinguishes fire, fire melts metal, and metal chops wood.
The generating cycle of elements also mirrors the cycle of life. The vitality of wood symbolizes birth, fire represents the rapid change and vigor of youth, earth represents the stability of adulthood, metal symbolizes the decline of old age, and water represents death.
The interaction of the elements influences both mystical and mundane study. Onmyōji, practitioners of the mystical art of onmyōdō, strive to keep the elements in balance in order to insure that the cosmos runs in an orderly fashion and to bring about good fortune. Shinkan pay homage to the five elemental guardians of Tsurukoku, to secure their favor and protections. The interaction of the elements is also prominent in other traditions, including music, medicine and art.
In medicine, for example, each element is associated with a system of the body: wood is associated with the liver, fire with the heart, earth with the spleen, metal with the lungs, and water with the kidneys. When the elements within a person fall out of balance, either through exposure to negative energy, or through over-exposure to one element, illness develops.
A person with weak lungs, exhibiting shortness of breath and a persistent cough, would be treated by increasing their exposure to herbs associated with earth, in order to reinforce the metal element of their body. By contrast, someone with a high fever would be treated with liquids and herbs associated with water, in order to diminish the overabundance of fire in their body.
The interaction of the gogyō can be seen in indigenous martial arts. Each art categorizes its maneuvers within the various elements. Locks and throws entangle, so are categorized as wood. Rapid kicks and punches are explosive, and so are categorized as fire. Blocks and defensive postures are categorized as earth, as they ground the artist. Metal techniques include powerful strikes, which chop down an opponent. Water techniques are those that use an opponent’s power against him.
The martial artist uses the appropriate element to overcome his opponent’s techniques. He would use water maneuvers to redirect the rapid blows of a fire technique, or use the locks and throws of wood to overcome the defensive posture of an earth technique.
The five elements appear in the Tsurukokan calendar, as each element lends it attributes to a given year. A wood year is filled with growth and opportunity; a fire year is filled with turmoil and change; an earth year is peaceful and balanced; a metal year is filled with division and destruction; and a water year is filled with stillness and death.
Adventurers study the gogyō as well, for they rely on the interactions of the elements to help them defeat adversarial creatures. Many creatures have a strong affiliation with an element, such as the aburaakago, which is composed primarily of fire, or the kappa, which has a natural mastery over water.