天地無用!
The 1999 series "Dual! Parallel Trouble Adventure" is related to the "Tenchi Muyo! Ryo-ohki" universe, due to the blatant use of the "Lighthawk Wings" associated with the Jurai dynasty in "Tenchi Muyo". The creator of both "Dual!" and "Tenchi Muyo!", Masaki Kajishima, confirmed that "Dual!" does relate to "Tenchi Muyo!", and is in fact an alternate version of the "Tenchi Muyo!" universe. Guardians of Order published a line of English-language "Tenchi Muyo" role-playing game books based on the various series in the Tenchi franchise starting in 2000.