Fumihiro Joyu is one of the highest-ranking members of Aum and one of its only leaders not charged with a role in the 1995 subway gassing, the Associated Press reported.
Virtually all of the groups former leaders, including guru Shoko Asahara, are currently on trial or in prison. Joyu is expected to fill a leadership vacuum within the still potentially powerful group.
"I intend to return (to Aum), but as I have just been released from prison, I am completely unaware of the situation around me, and at this point therefore have no comment to make," Joyu said in a statement.
Joyu was arrested in 1997 for forgery and perjury in connection with a land deal made by the group and sentenced to three years in prison.
Aum is believed to have 2,000 followers throughout the country.