Ep. 3: Time for Ultimate Girl to Die! Tokyo Is Annihilated!

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The girls learn that their power comes from being embarrassed (because their costumes keep gradually disappearing until they are naked), and the more embarrassed they become, the stronger they become. Vivienne immobilizes the alien, but it breaks free. The girls learn that the core of the alien must be destroyed. Silk transforms and defeats the alien. Silk thinks Vivienne is mad at her and also has a crush on Makoto, Tsubomi's older brother. (Source: Wikipedia)