Kaoru Hino is Yamato Hino's younger sister in the anime. She has slightly messy black hair and brown eyes. Transported to the ancient kingdom of Mu, she dons local attire including a tiara and Mu-styled dress.

Naturally curious, especially about Mu's unfamiliar surroundings, she documents her experiences through frequent photography. She shares a close bond with her brother, immediately agreeing to donate blood for a critical transfusion when he is injured in battle. Their rare shared blood type necessitates her journey to Mu. There, she befriends Madoma, aide to Queen Aila.

During her stay, Kaoru accompanies Madoma to explore Mu, seeking answers about why Yamato was summoned as God Mazinger's pilot against the Empire of Dinosaurs. Witnessing the robot in combat eases her initial safety concerns. Later, the shapeshifting antagonist Yoname kidnaps Kaoru, impersonating her to infiltrate Mu and capture Aila. Bound and silenced during captivity, Kaoru eventually escapes. Returning to Mu, she alerts Madoma to Yoname's deception, helping uncover the impersonation plot targeting Aila.

Her narrative concludes when she is sent back to her original 20th-century time period, securing Yamato's promise to return home eventually. She exists solely within the anime adaptation, absent from manga, novels, or other franchise media. Her role centers on familial connection, advancing plot points involving Yamato's vulnerability and Yoname's infiltration scheme before departing.