Taiki is a tenth grader at Juuban High School and is the most intelligent among the trio, beating Ami Mizuno in exams and gaining the highest scores. Taiki is the only one among the trio who genuinely enjoys her disguise, as well as the high school she attends. She is a member of the Literature Club and enjoys poetry.
According to Naoko Takeuchi, she gives the impression of a "cool, reticent Setsuna", but is not very understandable. Although she has good eyesight, she wears glasses at times.
Taiki has a typical poker face, long brown hair tied into a ponytail and long fingers. She has brown eyes.
As a member of the Three Lights, she wears a light green shirt with a blue tie and a light brown coat with a white rose.
The name "Taiki Kou" means "atmospheric light" (taiki kou).
- The Materials' Collection shows that Taiki and Setsuna are about the same height.
- In the Mixx manga, her name was changed to Taiki Lights, implying to the Three Lights.