A mythical Kaiju that lives deep in Iida Mountain. Woo only appears when it is called by Snow Girl, a human girl, or when she is in danger. Although not violent by nature, Woo does not hesitate to attack if the Snow Girl is involved with trouble.

Woo was first sighted when it appeared to scare people away from a mountain village where the Snow Girl was scolded after getting in the way of a veteran hunter Machimura. People in the neighboring towns asked the SSSP to investigate and Hayata, Ide, and Arashi headed for Iida Ski Resort. They encounter Woo, but it disappears when it hears the Snow Girl cry out.

The townspeople mistakenly believe the Snow Girl is somehow controlling the Kaiju and chase her out of town, causing the Snow Girl to call out “Woo!”. It appears for a third time and begins to attack the ski resort.

Ultraman comes to the scene and begins to fight it, but in the end Woo disappears into the snow after hearing the Snow Girl call its name for one last time.