Tenchi Muyo! (天地無用!, Tenchi Muyō!?), is a Japanese anime, light novel, and manga series created by Masaki Kajishima and Hiroki Hayashi about a boy named Tenchi Masaki, which has grown into a larger franchise. Along with the likes of Moldiver, Tenchi Muyo! was one of the early successes for AIC, the animation company behind it, which went on to create El-Hazard, Battle Athletes, Oh My Goddess!, Dual! Parallel Trouble Adventure and many other anime series. The generally accepted translation of the title is No Need For Tenchi, though at the time of its appearance it was also translated variably as No Heaven and Earth and, bizarrely, This Way Up.

The original series, Tenchi Muyo! Ryo-Ohki, is a six episode Original Video Animation (OVA) released in Japan in 1992–93. As its popularity grew, it spurred a seventh episode (also known as the Tenchi Special) and a stand-alone Mihoshi Special. In 1994-95, the second OVA series (episodes 8-13) was released, featuring episodes 8–13. A third OVA series (episodes 14–19) was released from 2003-2005, followed by a special twentieth episode.

Source: Wikipedia