The Yin-Yang Theory is a fundamental concept of ancient Chinese philosophy, describing that all things in the universe are made up of two opposite yet complementary energies, yin and yang.
They continuously transform and bring balance.

In Yakuzen, it's believed that an imbalance of yin and yang affects human health.
The Yin/Yang Theory is essential for understanding body conditions, treating health issues, maintaining good health, and improving health.

You can check Yin and Yang Theory on Traditional Chinese Medicine World Foundation.