Juri Katou is a main character in Digimon Tamers and a classmate of Takato Matsuki, Hirokazu Shiota, and Kenta Kitagawa. She is a girl of about ten years old who initially presents a cheerful, sweet, and supportive exterior, often seen with a homemade hand puppet which she uses to speak for her in moments of social awkwardness or emotional distress. This puppet was originally a gift to entertain her much younger half-brother, but it also serves as a psychological tool for Juri, allowing her to retreat into a false, happy world and avoid confronting difficult emotions or situations directly. Her family runs a small restaurant or tavern in Shibuya, where she sometimes helps as a waitress. Beneath her sunny facade, however, Juri carries a heavy burden: her biological mother died from an illness when Juri was very young. Her father, unable to properly care for her due to his own grief, later remarried, but Juri was cold and unwelcoming to her kind stepmother, feeling that the new woman was trying to erase the memory of her birth mother. This history left Juri with a deep-seated belief that her life was governed by a cruel and inevitable "destiny," a word her father used when explaining her mother's death and one that would later haunt her.

Although she initially claimed to have no interest in Digimon, Juri secretly collected the trading cards and became one of the first people outside the main group to befriend Takato's partner, Guilmon. Her desire for a partner Digimon of her own was fulfilled when the heroic beast-man Leomon appeared and swore to protect her. Despite Leomon's initial reluctance, Juri persistently chased after him, and he eventually became her official partner, with her Digivice, a yellow D-Ark, activating soon after. In the Digital World, Juri proved to be a capable and creative Tamer. During a battle with the giant snake Digimon Orochimon, who had kidnapped her, she used a rare and powerful LadyDevimon card to modify Leomon, granting him the "Poison" attack and enabling him to destroy their enemy.

Juri's role in the story becomes critically important following the death of Leomon at the hands of the rogue Digimon Beelzebumon. Leomon's final words, repeating the idea that this was her "destiny," shattered her carefully maintained cheerful persona. She fell into a profound, catatonic depression, believing she was fated to be alone and that everyone she loved would be taken from her. This overwhelming despair made her the perfect host for the D-Reaper, a sentient, world-ending program. The D-Reaper used Juri's negative emotions as fuel, absorbing her body and creating a replica, Agent Juri, to learn about the human world while imprisoning the real Juri within its core. For much of the final arc, Juri is trapped inside the D-Reaper's Kernel Sphere, a captive audience to its torment, until she is finally rescued by Takato, whose determination and love help her find the strength to reject the D-Reaper's nihilism. By the end of the series, she learns to accept her past, forgives both her stepmother and Impmon (the Digimon who was Beelzebumon's partner), and realizes that people can forge their own paths and create their own happy endings.