Youko is a very loose and carefree person who does as she pleases, without much care for the people around her. As shown in the series, Youko leaves Touma in Japan because she feels there is no need to drag a daughter along to Paris. Also, Youko gave birth to Touma illegitimately, going to show how unrestrained she is.
Kazusa is Youko's illegitimate daughter. When Touma was young, Youko left her in Japan and moved to Paris, ruining the relationship between herself and her daughter. As Touma said, she had always aspired to be as great as her mother, but after her mother left her by herself in Japan, Touma's dreams disappeared. Youko does not view Touma very highly at all, and she regards her as a petty child. The relationship between mother and daughter is far from friendly, and cold at least.
- The name Youko means "light, sun, male" or "ocean" (you) and "child" (ko).
- Youko's surname Touma means "iron", "overturn, summit, origin" and "slaughter, butcher, slay" (touma). Each kanji means "east", "peach", "wisteria", "leaping up, jumping up, rising, advancing, going", "pupil (of eye)" or "bear, accept, undertake, just" (tou) and "true, reality", "horse", "dance" and "gate, counter for cannons" (ma).