Inuarashi, also known as Duke Inuarashi, is the canine member of the Mink Tribe and one of the two rulers of the Mokomo Dukedom on the back of the giant elephant Zunesha. He holds the title of the Ruler of Day, governing the kingdom from six in the morning until six in the evening, during which he is active and awake. Outside of these hours, he falls into a deep sleep.

His origin story is deeply intertwined with the samurai of Wano Country. As a child, driven by curiosity about the outside world, Inuarashi and his best friend Nekomamushi left their home of Zou. Their journey led them to the shores of Wano, where they were initially persecuted as strange creatures. They were saved by the charismatic daimyo Kozuki Oden, to whom they swore lifelong loyalty. Inuarashi became a retainer of the Kozuki Family and one of the Nine Red Scabbards, the elite group of samurai who served Oden. His dedication to Oden was so absolute that he and Nekomamushi secretly stowed away aboard the ships of two legendary pirate crews—first the Whitebeard Pirates and later the Gol D. Roger Pirates—to continue serving their master. After Oden's execution, Inuarashi returned to Zou but lived with the heavy burden of his lord's death.

Personality wise, Inuarashi is a stark contrast to his counterpart, Nekomamushi. He embodies a calm, noble, and deeply courteous demeanor. Inuarashi is a kind and benevolent leader who is deeply respected by his subjects for his wisdom and compassion. Unlike many warriors, he abhors unnecessary violence and prefers to resolve conflicts through diplomacy and rational discussion. This was most evident when the Beast Pirates invaded Zou; despite being the strongest warrior on the island, he offered to let them search for their target peacefully to avoid bloodshed. He is, however, unwavering in his convictions. His loyalty to his friends and allies is absolute, and he refused to betray the ninja Raizo even while being cruelly tortured by Jack, an ordeal that cost him his left leg.

His central motivation is the fulfillment of his oath to the Kozuki Clan. He lives to see the restoration of the Kozuki family and the opening of Wano Country's borders, a mission entrusted to them by Oden. This sense of duty drives him to endure a twenty-year rivalry with Nekomamushi, whom he blames for Oden's death, and to survive the brutal attack on his kingdom. He is also driven by a strong sense of honor and gratitude, as seen when he readily forms an alliance with the Straw Hat Pirates to repay them for saving his people.

Inuarashi's key relationships define his character arc. His most significant and complex relationship is with Nekomamushi, his childhood friend and fellow retainer. Once inseparable, their friendship fractured after Oden's death, leading to a bitter feud that split the governance of Zou into day and night simply so they would not have to see each other. They reconcile during the Zou Arc at the request of Oden's son, Momonosuke, agreeing to a truce to honor their late master. He shares a deep bond with the other Scabbards, particularly Kin'emon and Kanjuro, and holds an unwavering devotion to Momonosuke, whom he sees as his new liege. His relationship with the Straw Hat crew is one of deep gratitude, especially toward Tony Tony Chopper, who healed him, and Brook, whose skeleton form Inuarashi amusingly finds delicious.

Throughout the story, Inuarashi undergoes significant development. He transitions from a mischievous, stowaway child to a grief-stricken and angry ruler, and finally to a resolute and forgiving warrior. The Zou Arc sees him physically broken but spiritually unyielding, while the Wano Country Arc shows his reemergence as a formidable fighter. His lowest point—losing his leg to torture—becomes a testament to his will, and he later adapts by using a sword as a prosthetic, transforming a weakness into a new weapon. His journey culminates in the Raid on Onigashima, where he fully reconciles with Nekomamushi and achieves personal vengeance by confronting and defeating Jack, the man who decimated his homeland.

As a fighter, Inuarashi possesses immense physical strength and mastery over several rare combat abilities. He is an expert swordsman, wielding a blade with great skill, and later adapts to a unique two-sword style using a blade attached to his prosthetic leg. As a member of the Mink Tribe, he can generate powerful electricity through a technique called Electro. He is also a proficient user of both Armament Haki, which is known as Ryuo in Wano, and Observation Haki. His ultimate transformation is the Sulong, or Moon Lion, form. By staring at a full moon, he can release his hidden potential, transforming into a larger, more bestial form with white fur and red eyes. In this state, his speed, power, and electrical attacks are amplified dramatically, allowing him to overwhelm powerful ancient zoan users like Jack.