Uniform Stealing Board

At 11:30 or so, one of the heroines is kidnapped by the villainess. Later, around 30 minutes in, the heroes seemingly find her tied up with a bag over her head, but she turns out to be an assassin in the heroine's stolen dress.
https://www.youtube.com/watch?v=4QZm2TSiqg0

Around 3:30 into the next episode, the heroine is found tied up, now dressed up in a different outfit after her dress was taken by the impostor.
https://www.youtube.com/watch?v=ojIjVrvA-xg