Kou (降) is Cloud Gouger’s water or mist. The catalog is blunt: it exists to make Mei a wire and Yui a larger freeze. Readers who only clip lightning miss the humidity the bolt is using.
Setup as a named technique
Most blades have three named techniques. Kou is the one that looks like weather instead of a finish. Sojo still spends it as a customer. Chihiro still spends residual charges as a partner. Same third word. Official chapters: VIZ / MANGA Plus.
File: Mei, Yui, Cloud Gouger.