There are very little sites that have this creature. The following information is from Shin Megami Tensi wiki. If this is breaking some rules please aid me in supplying more information on this creature.

According to scripture Zi-bu-yu in Qing dynasty, Hua Po is a kind of tree spirit said to be formed from the disembodied souls of dead humans when three or more people hang themselves from the same tree. They appear as beautiful young girls that are dressed in white clothes but are much smaller than the average human. Although they cannot speak, it is said that they make sounds that are as beautiful as those of songbirds.

I have also seen information that says they are nude pale white women the size of a fairy.