An Akita dog originally named "Hachi" because the Japanese character resembles a fan symbolizing a wide-open future. He has a thick double coat of light brown fur with a white patch on his face. Bred from a line of bear hunters, he possesses immense intelligence and a stubborn streak, learning commands easily but selectively choosing when to obey them.

Yasuo is a five-year-old boy who commutes through Shibuya Station. Outgoing and curious, he takes an immediate liking to the golden-brown Akita he meets on the train platform. As he grows older and begins traveling to school alone, he develops a profound sense of responsibility toward the dog and learns to emulate traditional values of dedication and perseverance.

A scholarly man who teaches agricultural science at Tokyo Imperial University. He is a man of strict habit and routine who takes great joy in raising his new puppy, treating the animal with immense affection and respect. He intentionally structures his daily schedule around the dog's training and feeding, creating a deep bond built on mutual understanding.

The pragmatic station master of Shibuya Station in Tokyo. He manages the bustling railway hub with a strong sense of duty and takes a personal interest in the daily commuters. He acts as a wise elder figure within the community, offering practical guidance to younger travelers and ensuring the station runs smoothly.

Yasuo's mother, who travels with him on the train during his early school years. Initially cautious about letting her son interact with a large Akita, she soon recognizes the animal's gentle nature. She guides her son's early interactions at the station and supports his growing sense of empathy.

Yasuo's father, who helps guide his son's understanding of duty. He provides practical wisdom about the nature of Akita dogs, explaining their history as bear hunters and their strong survival instincts. He uses these facts to teach his son about the severe responsibilities of caring for an animal.

A local merchant who sells chicken skewers near Shibuya Station. He becomes part of the community that marvels at the Akita's intelligence, generously offering his food to the dog after witnessing the animal's unique ability to eat meat directly off the skewers.