Xenosaga: Pied Piper is a side game in the Xenosaga series that takes place 100 years prior to the start of the first game. The game focuses on the backstories of various characters in the series, notably Ziggy and Voyager. Told in three chapters, the plot revolves around Ziggy, at the time known as Jan Sauer, as his investigation unit works to stop a serial killer. Battles use a similar system as the one found in Xenosaga Episode I.