Sadaharu is a massive white-furred canine-like creature, standing roughly 170 cm tall when seated and weighing approximately 300 kg. He wears a red collar and maintains canine habits such as walking, eating, sleeping, and defecating in unsuitable places. His diet consists of seven bags of dog food per meal, supplemented by consuming non-food objects like plastic figures or cell phones, causing financial hardship for his caretakers. Originally an Inugami (Dog God) embodying attack and destruction, he guarded Earth's Dragon's Pulse (龍脈 ryūmyaku) at the Dragon's Lair (龍穴 ryūketsu) with the priestess sisters Ane and Mone. The Amanto (alien) Space Terminal's construction over this energy source rendered his role obsolete, leading to his abandonment due to the sisters' financial inability to sustain him. He was left in a cardboard box outside the Yorozuya freelance business, where Kagura found and adopted him in Episode 10, naming him after her deceased pet rabbit "Sadaharu No.1". Initially aggressive and defiant, Sadaharu habitually bit people's heads, focusing particularly on Sakata Gintoki. He disobeyed commands and caused disruption through unprovoked attacks and destruction. His demeanor gradually softened over time, developing loyalty to the Yorozuya members—Gintoki, Kagura, and Shimura Shinpachi. He formed his strongest bond with Kagura; her physical strength allowed her to resist his bites, which she interpreted as affection. He demonstrated protective instincts towards her, transforming violently when she was harmed. Despite becoming calmer, he retained wariness around strangers and occasional destructive tendencies. His abilities include exceptional speed, strength, and agility, enabling him to run at vehicular speeds, scale walls, and carry multiple people. As a guardian deity, he could suppress the Dragon's Pulse energy, though this required existing in a sealed state between life and death. Consuming strawberries and milk (e.g., strawberry milk) triggers a transformation into a larger, horned monster exhibiting heightened ferocity. Reverting necessitates a ritual involving a genriki-infused baseball traced in a five-pointed star pattern. His counterpart, Komako, shares similar transformative capabilities. Key story involvements include: - **Inugami Arc**: Exploration of his origins and role as a guardian deity, revealing his connection to Ane, Mone, and Komako. - **Kintaro Arc**: Assisting in transporting a dying alien to reunite with his master while evading pursuers. - **Kintama Arc**: Remaining unaffected by memory-altering technology and aiding Gintoki in restoring the Yorozuya's memories, promising to advance without hesitation during their assault on the Kabuki District. - **Rakuyou Arc**: Comprehending Kawakami Bansai's samurai resolve, carrying Shinpachi toward Gintoki against initial objections. - **Silver Soul Arc**: Sacrificing himself to stabilize Earth's Altana energy, entering a two-year comatose, crystallized state. He revived upon hearing Kagura and Shinpachi's calls during the Terminal battle, saving them from a fall and participating in the final conflict before returning to his normal form. His relationships involve viewing Kagura as his primary caretaker and emotional anchor, tolerating Gintoki despite frequent head-biting, and accepting Shinpachi as a secondary caretaker responsible for feeding and cleanup. He considers Elizabeth a rival for mascot status, engaging in competitive clashes but sometimes collaborating. Trivia notes suggest his name may reference Sadaharu Oh or Teiji Inui, though the specific inspiration is unconfirmed. The "haru" (spring) in his name potentially alludes to strawberry season.