Sergei was a former KGB Agent.
Sergei finished second in the KGB Academy to Natalya and asked her to quit. He joined up with Crypto and Nataya in Albion to defeat the KGB. Sergei was despised by Crypto because he thought that Natalya and him were in a relationship. Sergei thought the same about Natalya as Crypto did, but she didn't show the same feelings. Despite that, he harbored no animosity towards Crypto.