Natsumi Orifushi shoulders the responsibilities of the eldest sister in the Orifushi family after her parents' death, managing their Min-Min Ice Creamery business. She spearheads the shop’s operations and its annual rivalry against competing stores, particularly the emerging threat of 101 Ice Cream. Standing 165 cm tall with a slim build and pale complexion, she possesses violet hair styled in a long ponytail with spiky bangs and an ahoge, typically reaching waist-length or beyond. Her tareme-shaped green eyes convey gentleness, while her figure measures 107-56-90 cm. She favors practical and traditional attire like aprons, kimonos, maid dresses, and sandals, often accessorized with ribbons in her hair or on her body, and a cross necklace.

Natsumi maintains a consistently calm, kind, and refined demeanor, speaking gently and politely while embodying a relaxed, docile presence. She extends her caregiving nature to her younger sisters alongside business duties. Her personality undergoes a drastic shift when exposed to alcohol; even its scent induces tipsiness, and consumption triggers an aggressive, frenzied state. She holds a keen interest in fortune-telling, employing unconventional yet surprisingly accurate methods to predict fortunes for herself and others.

She interacts closely with protagonist Shiki Haruomi, affectionately dubbing him "Haru-chan," and navigates multifaceted roles as his coworker, potential girlfriend, and sister figure. Orphaned young, her life revolves around upholding familial obligations through business stewardship and sisterly guardianship. Her core traits—managerial dedication, alcohol sensitivity, fortune-telling hobby, and dual personality states—persist consistently across her appearances in the original visual novel, sequel *Dokidoki Full Throttle*, and OVA adaptation.