Sergei is 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. He is despised by Crypto because he thinks that Natalya and Sergei are in a relationship. Sergei thinks the same about Natalya as Crypto does, but she doesn't show the same feelings. Despite this, he harbours no animosity towards Crypto.