7 episode OVA series running from 2010-14, adapted from the 10 volume novel series by Harutoshi Fukui. Occurs in U.C. 0096, three years after Char's Counterattack.
The series revolves around the pursuit of Laplace's Box, a MacGuffin said to contain a secret that could bring down the Earth Federation government, by Neo-Zeon remnants calling themselves "The Sleeved" and Londo Bell, the special taskforce from Char's Counterattack. The titular Unicorn Gundam acts as both a map and key to the Box, coordinates to which are encrypted in its operating system.
