When psions were fairly new to Jaern, a few gifted individuals picked them up and began finding others that had the gift in order to teach them. Eventually this basically became a psion school and grew in size in the capital city, Vesuna. After the school was established, a plague hit the city which had a symptom of making the infected person lose their mind while infected, some infected people ended up killing their own family members or themselves, even though the infection wasn't fatal and went away on its own in a few weeks. People looked for someone to blame and since the infection effected the mind, the town's people pointed their fingers at the psions. As the plague began impacting the city and the psions seemed to be immune to the plague, the number of town's people against them grew and grew. The town officials didn't do anything to alleviate the problem and the impeding violence forced the psions out of Vesuna. They went southwest and settled in the location now known as Usumi. Soon after settling, they spent effort to fortify the city fearful of violence against them, by the town's people of Vesuna or even the officials looking to deal with fallout from the plague by blaming it on them.
Uzumi is basically a heavily fortified Psionic school with a town around it. Since it's founding, the city has been very wary of non-psions and they will test people that wish to enter for psionic potential. People wishing to enter the city that don't have psionic potiental must be escorted at all times and are only allowed to visit select locations in the city. Failure for non-psions to comply will result in expulsion from the city, incarceration, or hostile actions against them.
While worship of deities is not forbidden within the city, the city doesn't permit large temples being erected for any particular deity. Therefore, worship is generally done in private and very few priests live in the city itself. Psionics and natural medicine are the primary method of healing and treating the sick.
The city of Uzumi is based primary around the psion school at its center. Therefore, the city is largely run by the council of psions that are in charge of school business.