As seen in K-ON!, Death Devil is the fictional heavy metal band fronted by Yamanaka Sawako (stage name: "Katherine", lead guitar and vocals) when she was in the Light Music Club in high school. The other members of the band are:
This tag covers the members of the band seen together, various versions of Death Devil stage costumes including Sawako's mask, and the main K-ON! characters wearing their costumes from season 2 episode 10, when they appeared on stage together with Death Devil.