Kyōko Machi, a teenage dullahan, exists with her head permanently detached from her body. A blue or green flame flickers from her neck, linked internally through an "another space" wormhole-like structure that enables breathing and digestion despite physical separation. She must carry her head in her arms constantly, preventing hand use for other tasks. This condition manifested unexpectedly during her toddler years after initial normal development.

Physically, she has fair skin, short spiky orange hair maintained for practicality, blue eyes, and a tall, developed physique for her age. Her arms grew muscular from head-carrying, occasionally causing accidental contact with her chest while walking. During summer, she wears a sweatervest over her uniform to reduce sweat visibility on her shirt.

Kyōko displays a reserved yet patient, diligent personality. Academically accomplished—ranking fifth in midterms and first in proficiency exams—she conveys emotions through body language. Seeking physical contact like hugs or hand-holding compensates for isolation, and she dislikes solitude, enjoying being carried or cradled by trusted individuals. Her neck flame heightens when flustered.

Daily adaptations include balancing her head while moving, using backpacks accommodated by her school via Tetsuo Takahashi, managing overheating in warm weather, and handling tasks requiring both hands. Early social interactions were strained by others' discomfort with her appearance, though she wished to joke about it openly.

Key relationships drive her growth. She nurtures a one-sided romantic interest in Takahashi, her biology teacher, appreciating his kindness and non-judgmental support—such as holding her head upon request. Close friendships include Hikari Takanashi (despite annoyance at her mischief), Yuki Kusakabe (after resolved misunderstandings), and Sakie Satō, with whom she shares romantic confidences. These bonds gradually bolster her confidence and reduce social anxiety.

Her development shifts her from shyness to proactively pursuing dullahan biology. Inspired by Takahashi’s scientific approach, she aims to become a researcher unraveling her species’ mysteries, including theoretical dimensional studies for head reattachment. This ambition reflects her acceptance of identity and desire to advance demi-human understanding.