In the middle of the Meiji era, Japanese painter Rogin goes on a trip to draw a bijin-ga, and he accidentally rescues a salt merchant. The salt merchant describes an out-of-this-world beauty he once loved. This is the prologue to the drama “Suiko,” a tale of humans and nature.

Ayami Kawaguchi is a 17-year-old high school student. Her family runs a tofu shop where the tofu is made with local spring water. She is a member of her high school's kyudo club, but she doesn't do well there. One day, Ayami delivers tofu to a local sake brewery. There, she finds the owner of the sake brewery, Shozo Sugita, collapsed and he is sent to hospital. Afterwards, Ayami Kawaguchi gets involved in a dispute over the water source succession.

The eighth shogun, Tokugawa Yoshimune, fights against evil rampant in Edo while blending in with the common people as Tokuda Shinnosuke, the third son of a poor samurai retainer, commonly known as "Shin-san". The story depicts Yoshimune, who is shaken by the issue of succession, the drama within Edo Castle, and a difficult case involving a conspiracy that occurs in the castle town, with the addition of new characters and a sense of the era.