Zu-Zain-Da

Zu-Zain-Da appeared in 2000 TV series called Kamen Rider Kuuga. Zu-Zain-Da (ズ･ザイン･ダ Zu Zain Da), otherwise known to the police as Unidentified Life Form #22 (未確認生命体二十二号 Mikakunin Seimeitai Nijūni-gō) and B3 (Ｂ群３号 Bīgun Sangō), is the leader of the Zu Group of Gurongi. Zain is able to assume the form of a hulking strongman with a temper to match his brawn.

Soon after the Me Group's turn begins with the Zu no longer worthy to play, and when their first hideout got compromised by the police's smoke bombs, Zain starts acting on his own by attacking trucks and jabbing the drivers to death with his horn.

He overpowered Kuuga in both human and Gurongi forms when Biran intervened as Zain stole his turn. While Zain resumes his attack on large motor vehicles, Yuusuke manages to perfect his Mighty Kick to finally kill the rampaging Gurongi, breaking his horn in the process.

At least one Zu-Zain-Da was part of a group of human-turned Gurongi created when they were exposed to N-Gamio-Zeda's miasma. Some were later absorbed by him in a last effort to defeat Kuuga and Decade. The remaining Gurongi died after Gamio was defeated.

He had a brief appearance as one of the monsters who captured Ankh and Momotaros.

Zain was one of a trio of Gurongi (with Zu-Gooma-Gu (Ultimate Form) and Me-Badjisu-Ba) who were seen fighting Kuuga in new video footage that Tomoko Nozama found on the internet, along with other clips of past Kamen Riders, who are now known as urban legends.

Zain is destroyed by Faiz's Sparkle Cut.