From the pages of Wasyu's Encyclopedia Tenchicca--
Tenchi Muyo! in LOVE tells a tale of how the TV-based Tenchi gang traveled back in time on a mission to rescue Tenchi's mother, Achika, whose life is in danger due to the recent escape of Kain. Kain is an entity of pure energy who was captured by the joint forces of Galaxy Police and a former Emperor of Jurai in the past. Destroying the GP Headquarter upon his escape, Kain now seeks vengeance on all members of the Juraian Royal family, including Achika.
Achika's survival will ultimately determine the fate of the Tenchi family in the present time.