- Young Subaru (Takaaki Kuwajiro) and Shizuku (Sara Kitamura) lived with their mother Natsuko (Sachiko Sakurai) in Tokyo. Because their mother became sick and hospitalized, the children had to live with their father Daiji (Eiichiro Funakoshi) in Hokkaido. Subaru and Shizuku's parents divorced five years earlier.
Their father Daiji works as a veterinarian in a wild animal shelter. Although the children are surrounded by their beautiful natural surroundings, they are confused because their father spends little time with them. Their aunt Chie (Kyoko Fukada) - who is a wild animal photographer - and Takuma (Masaru Hamaguchi) - who works on a ranch - takes care of the children. As the children's loneliness fades away, they come across a puppy that resembles a baby wolf. Shizuku feels an instant bond with the puppy, because the puppy is also away from its mother and decides to keep the animal as a pet. They named the puppy Ululu.
Then one day, molecular biologist Hasebe (Ken Mitsuishi), who works for a wild animal protection organization, visits Daiji's home. Hasebe informs the children that Ululu is most likely a baby Ezo wolf & must be taken in for protection as an endangered animal. Subaru and Shizuku then thinks if Ululu is taken, he will never come back and, instead, the children decide to take Ululu back to its mother ...