Tenchi Muyo Wiki
Tenchi Muyo Wiki

Washu explains the Mass

The Masu ( マス, Masu), known as Mass in the English dub, are a powerful aquatic species that originated on a planet 23,000 lightyears from Earth. However, scientific genius Washu Hakubi kept a number of them in a tank in her lab, and there may be more in unseen tanks. Very odd creatures -- basically just clumps of base matter -- the Masu are entirely nonviolent. However, when they recognize a threat, they can do incredible amounts of damage in self-defense.

Ryoko was made by Washu combining her own egg cells with Masu, and Ryo-Ohki was made by combining Masu with some kind of mineral lifeform.


Mass Diagram

Mass Diagram

The Masu are overall pacifistic and shy. They are naturally nonviolent, but easily frightened, and if they feel threatened, they can cause great destruction while protecting themselves. They act with a type of hive mentality -- the leader of Masu groups is recognized as the "brain," directing them in their decisions. This hive mind is different from that of bees or ants, however, because the queen, or "brain" in the Masu's case, is the nearest individual with the strongest emotions. So, if a member of another species was found to have stronger emotions than the current brain, then they would become the new brain of the Masu group.

Other than this information, it is unknown what Masu eat, the specifics of how they interact with each other, or how they reproduce.

Tenchi Muyo! Ryo-Ohki

The Masu first appeared in episode 10 of the OAV 2's, I Love Tenchi. The Masu are first drawn to Ryo-Ohki, sensing her heartache over a blossoming crush towards Tenchi. In response, a set of Masu inside a tank Ryo-Ohki had stopped by fused into the shape of a beautiful woman and broke free, intending on confronting Tenchi to help him in the fields. The creature seemed harmless towards Tenchi as it started gardening with him, but when Washu and the other girls arrived, warning him of what it could do, Tenchi panicked and tried to run, triggering the Masu's defense reflex. With Ryoko's timely arrival, the Masu's attack is deflected onto her, allowing Ryo-Ohki to pounce on top of them and, at Washu's command, assimilate with the Masu. Doing this granted the cabbit its ability to take humanoid form.


  • The Masu are said to be comprised of the matter, the "neutral matter," and the "antimatter."
  • Masu live in groups, rather similar to either a pod of dolphins or a pack of wolves; they follow a single leader, apparently the one who exercises the most inherent willpower, making that individual the "brain," guided by that individual's desires. However, should they identify an outside individual as having a stronger will than that, the Masu will make them the "brain" and act on their emotions.
  • When threatened, the main attack method used by the Masu is to propel bundles of their own composition at impressive velocity; enough to drastically reshape the landscape and total a sizable spaceship. (Although, the latter might have possibly been done in multiple attacks)


  • The Masu seem to be capable of amalgamating their bodies into new shapes; in the series, they took the (rough) form of an attractive woman while acting on Ryo-Ohki's will.
  • The other girls often refer to the Masu as Ryoko's father, much to her annoyance.