Goliath is the Yozakura family's pet guard dog, a member of a special breed known as the Okami, or Great Divine Dog, which has been continuously refined since the mid-Edo period. This breed was created specifically to protect the Yozakura lineage, and Goliath has served the family for over a hundred years, having been present since the time of Mutsumi Yozakura's great-great-grandmother. He appears as a small black dog with fur that has a faint blue tint and bright neon lime-green eyes, but he possesses the ability to change his size dramatically. He can shrink to a tiny form of about thirty centimeters, assume a middle form around one meter tall, and grow to a massive eight meters in height, large enough to carry multiple people on his back.

Goliath's primary motivation is the protection of the Yozakura family. He is fiercely loyal and will not allow anyone he does not trust to sit on him or hold his leash; only the current head of the family is permitted to ride him. In battle, he is highly aggressive toward anyone he perceives as a threat, willing to use his own body as a shield to absorb bullets and explosions thanks to his exceptionally tough hide. Despite this ferocity, he is calm and composed when no danger is present. He possesses a high level of intelligence, understanding human speech, assisting in missions, and is even capable of driving vehicles and writing.

In the story, Goliath serves as a loyal companion and a powerful asset to the Yozakura siblings. Although he is not a central character in terms of dialogue or personal plot, he regularly supports the family during combat and espionage operations. His long history with the family means he is treated as a trusted member of the household, and he shares close bonds with all generations of Yozakuras. Over the course of the series, Goliath continues to demonstrate unwavering dedication, often stepping in to protect Mutsumi or other family members during dangerous encounters. His development is subtle, rooted in his deepening trust for new allies such as Taiyo Asano, whom he learns to accept as part of the family. His notable abilities include size alteration, immense physical strength in his larger forms, super speed, bulletproof durability, and a keen sense for detecting threats.