kz (pronounced "k-zet"), also known as RE:NDZ, is one of the pioneering producers behind Hatsune Miku's most memorable early songs. His debut track "Packaged" set the tone for what would become his signature sound: reverberant, synth-heavy technopop that showcases Miku's vocal range. Though he stepped back from regularly uploading to Nico Nico Douga after 2008, he continued creating for major projects, contributing "Far Away" and "Star Story" to the Project DIVA game series in 2009 and 2010.

kz is the driving force behind livetune, an amateur music circle that made waves when it self-released the Vocaloid album Re:package at Comic Market 73 in late 2007. The project caught enough attention that Victor Entertainment picked it up for a wider commercial release on August 28, 2008—a major milestone as the first Hatsune Miku album sold through a major label. The original livetune lineup included kz and kajyuki, though kajyuki departed in 2008 to join CAPCOM, leaving kz as the sole member moving forward.