12 (English version) 

Her father runs a bar.  She has siblings but only her brother has been seen.  When Juri was younger her mother died, this left her a bit scarred but she does not overload until leomon also dies.

Juri started out as an acquaintance of Takato and wasn't connected to digimon in any way.  When she finds out that Takato has Guilmon as a partner that changes, she apparently does a bit of research and spends a hefty sum of money on digimon cards, giving her a collection to rival every other.  This is a  fortunate thing because after a few mishaps Juri becomes the partner of Leomon, and may well have to put them to use, often and thoroughly.

Juri has a hand puppet that she carries around with her almost everywhere she goes, though her mad skills at ventriloquism are debatable.  The puppet is of the sock variety and appears to be a dog.  At first it is a mystery what its purpose is, but it probably helps her express herself by giving herself another person to say things she is reluctant to.

At first Juri has a hard time fitting in with the tamers, and really has nothing in common with Takato's friends, so for a while she is a bit in the middle with only her wish to be a tamer (which she hides really well) and her friendship with Takato to keep her connected with the Tamers. 

After Ruki offers to teach her how to play the digimon card game that changes and a friendship develops between the two girls.  Once Juri becomes a Tamer it becomes a bit more obvious since they are often seen hanging out together.  Like their digimon Juri and Ruki very similar to each other, though Ruki is a bit more dramatic in everything she does.  At one point Ruki does become angry with Juri and get in a pretty one sided fig but it is a one time thing as far as I know.

Little is said about Leomon's history, but it is known that he is a vigilante of sorts in both the real an digital worlds before he meets Juri.

Leomon is a hardened warrior who first meets his partner when he saves her and Calumon.  Juri, who has been trying to convince Calumon that they are Tamer and partner immediately drops this idea upon seeing Leomon and decides that she and Leomon were destined to be partners.  Unfortunately for her Leomon is harder to convince and after a long chase followed by a battle in which Juri realizes that her cards won't work, Leomon leaves.  All is not lost however, Leomon once again tries to save Calumon, from a different Deva, only this time fails.  Juri receives a Digivice and uses it to heal Leomon after the fight.

.:added after the fact:.

Leomon dies, killed an absorbed by Beezlebumon.  Juri was pushed over the edge by this and went catatonic, Takato was also pushed over the edge and went completely psycho, digivolving Guilmon to Megidramon and by doing this almost destroying the real and digital worlds.  Seeing Guilmon "turned into a monster" doesn't help and Juri is in shambles by the end of the episode.  It is great (in a yeah, how how angsty way).