The Yulan-jin are those Kuei-jin whose souls have been shredded by the torments of Yomi Wan and are, as a result, unable to inhabit their own body. As such, they are forced to switch their bodies at each Little Death or when their Chi supply runs low, with no control on what body they will inhabit after their rise. With each new body, their memories of their former existence fragment and they must begin their unlife, like they rose from it.
Yulan-jin rarely advance in their Dharma and most have no real power in Kuei-jin society - one cannot have respectable and responsible duties if one does not have a stable body, after all. As such, those Yulan-jin who have realized their affliction form societies of their own.