Yui Ota

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.

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.