The bassist of Girls Dead Monster, Sekine Shiori tends to abruptly improvise during performances, much to Hisako's chagrin. She likes playing pranks on people just to see the surprised looks on their faces. She plays a G&L L-2000 bass guitar.
Awesome cosplay by Rinami! The cosplayer actually looks familiar... I may need to look through my files to see if I missed tagging her photos on Cosplay Holic. Thanks to Warren for sending this!