Kotobuki is a white-haired girl with a pink right eye and a blue left one. As Ai does, she also has heterochromia, which explains her eyes' different colors. She is also affected by albinism, causing her hair to be white and her skin to be quite pale.
She wears a black turtleneck under a short-sleeved, cream colored sailor fuku with light brown stripes on the collar and a magenta scarf, with matching shorts.
It is revealed that, other than being Neiru Aonuma's Egg, Kotobuki was her friend in the past. She is the first Wonder Egg Girl to have been seen in the real world and even interact with a protagonist when alive.
She was born into a corporation called Japan Plati, which wanted to create individuals endowed with incredible intelligence and a high IQ level by the use of in vitro procreation. The two girls never knew their parents personally, having been selected for their genes. Her genetic makeup is identified as extremely rare, presenting the characteristics of heterochromia, albinism and high intelligence at the same time. The unique aspect of those makes her body being the source of many researchers' interest, which will cause several problems at her death. Kotobuki Awano became both a scientist and a doctor and took the post attributed to Doctor Seki unintentionally. She then met Neiru, her only friend among the corporation.
Kotobuki meet her friend, Neiru Aonuma one last time as a Wonder Egg Girl in the Egg World. Her trauma has taken the form of the doctor she took the post from. Her Wonder Killer is in fact a materialisation of her worries.The latter fears that her body, kept in a state between life and death in the real world by a sophisticated machine while her mind being already dead. She already knows that, her consciousness being gone, several scientists from the corporation she was created in and from the government will try to experiment on her body, because of her extremely rare and precious genetic makeup. That is why she asks Neiru, when in the Egg World, to shut down the system of the machine keeping her body alive.
- The name Kotobuki means "longevity, congratulations, one's natural life" (寿).
- Kotobuki's surname Awano means "Africa, flatter, fawn upon, corner, nook, recess" (阿) (a), "wave, breaker" (波) (ha/wa) and "field, wilderness" (野) (no).
- The kanji "波" is usually pronounced ha.
- Kotobuki's egg is registered as k‡;‡2?k6.