**Yumiko Kamiazuma**, daughter of Kiyoharu, resides in the auxiliary building of the Kamiazuma estate as the niece of family head Kiyotsugu Kamiazuma. She serves as the current host for the goddess Juna, a fusion resulting from severe physical and mental injuries sustained in a tragic childhood accident. This bond enables her to function in daily life despite deep psychological scars.

Her personality exhibits pronounced childlike traits: playful antics, easy distractibility, and a quickness to take offense, contrasting sharply with her adult status. This behavior frequently challenges her maid, Nene, who struggles to ensure Yumiko meets professional obligations. Despite these quirks, Yumiko possesses significant life experience and willingly shares her insights. Unbeknownst to her, she wields supernatural abilities: her writing as a novelist can manipulate space-time, alter weather, summon living beings, and influence reality based on her thoughts. These powers manifested solely after merging with Juna.

Yumiko is Tōka Kamiazuma’s mother. Her daughter's childhood death—attributed to an inability to withstand the power of a stone sword—led Tōka’s current incarnation to become a replacement figure. Yumiko displays an uninhibited and erotic demeanor, often appearing nude and engaging in inappropriate physical contact with Tōka or Momoka Kawakabe. She refers to herself in the third person and expresses a desire to return to high school, reflecting her resistance to adulthood.

Those around her tend to like her for her carefree and friendly aura, which positively influences others. She remains unaware of the full extent of her magical capabilities or their impact on the world.