Brain Drain is the eighth volume of The All-New Tenchi Muyo! manga series, written and drawn by Hitoshi Okuda.
From the back cover of the Viz Graphic Novel:
The gang plays host to a mad-scientist class reunion when Sara, an underclassman from Washu's academy days, crash-lands outside the Masaki shrine. Sara is just as dinky as Washu, almost as smart, and much, much klutzier. Surely no one this cute could have sinister ulterior motives... or could she? Either way, the reunion wouldn't be complete without a visit from Yume, Washu's evil rival for the title of Number One Genius Scientist in the Galaxy. And when the talk moves from fond reminisces of college life to present-day plans for galactic conquest, Tenchi and his friends have to save Washu from losing her mind... to a super-genius thief!
Chapters
In the English graphic novels, each book restarts the chapter numbering from "Chapter One," rather than continuing chapter numbering from book to book as is standard in the Japanese release. Unlike earlier volumes of Tenchi Muyo! manga, Viz did not release this volume as separate comic book issues.