The Jumi are a race in the Playstation game Legend of Mana. For the most part, they are a typical fantasy race: human enough not to look creepy, but with a few differences to set them apart. In this case, the differences are very colourful hair and jewels in their chests. Generally, the colour of their hair and their jewel (called a 'Core') match.
Classically, the Jumi lived together in the Bejeweled City, a gigantic tiered city that resembles a spiraled shell. So long as a Jumi's core remains in their body and undamaged, they enjoy eternal life, but in exchange for that they cannot reproduce: there are one thousand Jumi cores, no more. As well, because of their rather unique and somewhat creepy abilities, they were shunned by the rest of the world-- A Jumi's tears can restore a dead Jumi core to life, but anyone else who has the misfortune to be cried over by a Jumi turns to stone.
The Bejeweled City has one road that spirals up from ground level to the palace of jewels at the peak, passing through the living quarters of the rest of the Jumi as it goes along. The city is divided into several strata, and each Jumi is put in a category depending on the clarity of their Core. The Clods are the lowest rank, and they are basically the normal citizens. Above them there are the Half-Lucidia, followed by the Lucidia. These two ranks could be viewed as 'upper class' or low royalty. Finally, the highest rank is that of the Clarius. The Clarius is somewhat like the King or Queen of the Jumi, and lives in the palace of jewels. There can only be two Jumi identified as Clarius at one time1: A Guardian and her Knight.
However, in the 'modern day' world, things have changed: The Bejeweled City has been shattered and the Jumi scattered to the four winds, all at the mercy of Jewel Hunters and other who would cause them harm. Due to their recently tragic past, they are seen as bad omens and shunned by most people. In a related event, all of the Jumi have lost the ability to cry, and without that their numbers are swiftly dwindling from attrition. The Jumi travel in pairs, one a Knight and the other a Guardian.
In-game, the Jumi quest is one of the three arcing quests, and its symbol is a shining jewel. For the most part, it centers around Elazul and Pearl, two Jumi trying to restore the Bejeweled City, as well as Sandra the jewel thief, who is a collector of Jumi cores. The Bejeweled City area is created by placing the Jumi Staff artifact on the world map, and it carries with it a +1 to Shade and +2 to Aura of all the surrounding areas.
1 No, I don't think the game ever reconciles the 'Jumi can't reproduce' statement with the 'One Clarius at a time' one, because it's also stated that Jumi really can't change their strata... I think. It's been a while.