The Pantsu Brigade (PANTSU-団) are an organization in The World R:X, led by sentient Saika's Panties. The Pantsu Brigade annually puts out a lingerie-themed calendar available in print and via a digital version that works via the Face-mounted display.
The Brigade is notable for its fan-club. However there seem to be some confusion in the fan-club about Tsukasa's inclusion. Some fans theorize that Tsukasa's panties don't exist or they really are boxers.