Hana, a student attending a college on the outskirts of Tokyo, falls in love with a "wolf man" who has the blood of wolves in his veins. They move in together, and soon Hana gives birth to two “wolf children” who are half-wolf half-human. They name the older child, a girl born on a snowy day, Yuki ("snow"), and the second child, a boy born on a rainy day, Ame ("rain").

The family's humble but happy life suddenly comes to an end when the wolf man is killed. Hana promises herself that she will raise their children well on her own and decides to move into a dilapidated house in the countryside rich in nature, where the children can one day decide for themselves to be "human" or "wolf." There, she meets Nirasaki, who teaches her how to farm, and the other kind people of the village. Although her initial motive to move to the countryside was to stay away from the prying eyes of neighbors, she comes to appreciate the mysterious bond between people.

One snowy day, Ame almost drowns in a river trying to catch a kingfisher. After he is rescued, he excitedly recounts his first "hunt," and the experience brings on a big change in the timid boy. Meanwhile, Yuki, now six, wants to "be like everyone else" and starts attending the village elementary school after promising Hana that she will not "transform into a wolf in front of other people no matter what happens." However, provoked by an innocent comment from a transfer student, Sohei, she inadvertently breaks her promise. Yuki is heartbroken, thinking she can no longer stay at the school, and Hana kindly watches over her distraught daughter.

Ame, who enters school a year later, has a hard time fitting in. "Instincts of the wild" have awakened in him, and he is drawn to the new world he has discovered in nature. Yuki tries to convince him that "they should live as humans," and they get into a violent fight. Yuki, who had always been physically stronger than her younger brother, is now no match for him, and she is badly beat. Both Yuki and Ame have started to walk down their own respective paths in life. "This is what I wanted but why am I so worried?" Hana confesses her uncertainty to the photograph of the wolf man.

Then comes the fateful day when a terrible storm hits the village and the mountains. Despite Hana’s regret that she still hasn’t done anything for her children, Ame and Yuki face decisions that set the course of their lives.