Mach Sakai gets his hands on another gas blowback bullpup rifle, the KSC IWI Tavor 21 GBB.  This GBB bullpup features the markings of the IWI Tavor as this is a licensed version. You can use the existing KSC/KWA M4 gas magazines, apart from the IWI TAR 21 gas magazine that goes with it. Since it is a KSC version, rather than the KWA version this is limited to  0.98J to meet Japanese power limits.