Young Girl of the Blue Will-o-the-Wisp is the fifteenth episode of Ultraman Taro.
In Nasuno, fire keeps scorching the countryside. A young girl, Kaoru, is accused of arson by the villagers who doubt her pleas of innocence. ZAT sends Kotaro and Ueno to investigate. When they speak with Kaoru, she tells them that the real culprit is an invisible monster that killed her mother. The townspeople don’t believe her story, and when they try to arrest her, Kaoru flees. Kotaro follows her, only to discover the real source of the attacks is just as Kaoru described: an invisible monster, Miegon.
Ultraman Taro Volume 4 features episodes 14-17.