Rika Nonaka is Renamon's tamer.
Rika's mother is a model and wants Rika to do the same, but Rika doesn't want to. Her grandmother has more respect for what Rika wants. Prior to the events of Digimon Tamers, Rika's parents divorced.
Introduction to Digimon
Rika lost a Digimon card tournament to Ryo, causing her to hate him with a passion. However, Ryo was not present at the next tournament, which Rika won, and was known as Digimon Queen afterward. Because of this, many Digimon appeared to her asking to be her partner. When she said she wanted one powerful Digimon, Renamon became her partner.
Rika only wanted Renamon to fight, destroying as many opponents as possible and absorbing their data. Unlike Renamon, it made no difference to Rika whether they were good or evil, as evidenced when she told Renamon to kill Guilmon, she only viewed Digimon as data, and was impatient for Renamon to digivolve, but temporarily had second thoughts when Terriermon lost his mind digivolving to Gargomon and nearly attacked her.
Eventually Rika was nearly killed during the battle with Dokugumon, but Renamon took a hit for her, mortally wounding her. Rika felt sadness for the first time at the thought of losing Renamon, enabling her to digivolve to Kyubimon and destroy Dokugumon.
Following this, Rika began to form a slightly better relationship with Takato, when he asked her if Digimon disappear for no reason, although she didn't seem to feel much emotion at this despite what happened earlier. She traveled with Takato and Henry to save Guilmon from the digital zone.
When Rika was being attacked by IceDevimon, she told Renamon she didn't need her or anyone. Shortly after IceDevimon took her to his icy lair and told her that she was as cold as him, and wanted her as his tamer. Rika refused, regretting her words to Renamon. After Renamon returned and Guilmon destroyed IceDevimon, Rika decided she hates all Digimon and walked in opposite directions as Kyubimon.
It seemed the end of Rika and Renamon's friendship and partnership. Rika thought Renamon was only using her and didn't want her. She watched the battle between Renamon and the three Flybeemon, but didn't do anything, and left when it was over. She also watched the fight with Harpymon, and seemingly finalized her separation from Renamon. However, when Harpymon was about to kill Renamon, Rika realized she couldn't let her partner be stomped out of existence. Having left her digivice at home, she stabbed Harpymon in the back with a stick. When Harpymon tried to attack her, Renamon digivolved to Kyubimon and destroyed Harpymon. From here, Rika and Renamon officially recognized each other as tamers, and their friendship became stronger.
In the following episode, Rika told Renamon she couldn't remember what she was so angry about half the time and didn't feel like making fun of Guilmon and Terriermon anymore.
Enter the Devas
When Mihiramon nearly killed Renamon, Rika couldn't believe she ever thought Digimon were nothing more than data. She also participated in the battle with Sandiramon, and later gave Renamon an "energy drink". After Renamon returned to the digital world with Vajramon, Rika was left to wonder whether she would return. Her mother had a photographer, Coco, take pictures of her, but when he proved to be too weird for her, she attacked him and ran. Eventually Renamon and Vajramon returned, and Rika received a blue card and used it to matrix digivolve Renamon to Taomon, who destroyed Vajramon.
Battle of Adventurers
The Devas, continued
After the battles with Indramon, Kumbhiramon, and Vikaralamon, Rika traveled with the other tamers to the digital world to rescue Calumon from Makuramon. When the Jagamon killed Meramon, Rika became angry at them. Later, Rika, Renamon, Kazu, and Kenta were hit by a data stream and teleported to another area where Jijimon and Babamon lived. Eventually they returned to the tamers flag they used to mark the spot where they arrived, but when they became tired of waiting for the others, they left, only to be swallowed by another data stream.
This teleported them to the clock area of the digital world where Rika inadvertently released Megadramon by setting the position of a clock. Kyubimon was nearly killed but was saved by the arrival of Ryo and Cyberdramon. Rika still hated Ryo and refused to go with him even when he offered to take them back to Takato and the others (though Kazu and Kenta accepted the offer). However Renamon thought they should have gone with Ryo.
While following the DigiGnomes to a river in the forest area, Rika was swept away by a wave of water, from which she was rescued by Calumon, who had escaped Makuramon twice. After another wave of water sent them back to the desert, the three reunited with Takato and the others. However, Caturamon captured Calumon and separated Takato, Henry, and Terriermon from the group.
After the battle with Orochimon, Rika and the others were sent to the Land of the Sovereign by a data stream controlled by Caturamon, reuniting with Takato, Henry, and Terriermon, who were fighting Beelzemon. After the battle with him, and going into the battle with Zhuqiaomon, Takato told Rika about pretending to be her and sending an email to her mother and grandmother. Although initially appreciating this, she became annoyed at the idea that Takato put a heart at the end of the email, which he did.
After the fight with Zhuqiaomon, Rika and Renamon made their way down the pit to rescue Calumon from the D-Reaper. Once they, Ryo, Cyberdramon, and Calumon became trapped by the D-Reaper, Rika and Renamon took a leap of faith into the chaos pit and biomerged to Sakuyamon, who temporarily defeated the D-Reaper and rescued Calumon.
As the tamers were returning to Earth on an ark, Rika and Renamon went back for Impmon, as they wanted to protect everyone after becoming Sakuyamon. They later got on board the ark, and Kazu called Rika "crazier than catfish" for risking staying behind in order to save their former enemy.
After arrival on Earth, Rika biomerged with Renamon often to fight the D-Reaper. During the final battle, Justimon, the biomerged form of Ryo and Cyberdramon, told Rika to transfer her energy to him in order to defeat the unstoppable Cable Reaper. Rika, speaking separately from Renamon, was reluctant, as the force of this could potentially kill Justimon. Ryo told her there would only be "one less annoying person to make fun of (her)". Having put aside most of her hate for Ryo, Rika was sure he was trying to impress her, and eventually transferred her energy. He survived.
Rika was temporarily separated from Renamon when Juggernaut's effects forced the Digimon to return to the digital world, but was later reunited.
The battle with Locomon took place on Rika's birthday. Rika got on Locomon with Takato and Renamon. When Takato mentioned that Yamaki was going to help, Rika didn't trust him, for unknown reasons. She became possessed by Parasimon's brother, at first making her sing a beautiful song, then making her attack Takato and Renamon, until Guilmon destroyed the Parasimon. Later the main Parasimon tried to possess her, but was foiled by Gallantmon, who severed his tentacles. For the final part of the battle, Rika and Renamon biomerged to Sakuyamon to fight the army of Parasimon.
After Parasimon's demise, Rika's birthday party was held. When Kazu mentioned Rika singing she walked outside to watch the sunset.
Rika's personality changes drastically throughout the series. Initially she only thinks of Digimon as data rather than living creatures, and all she wants Renamon to do is fight, destroy as many opponents as possible, and absorb their data, even telling her to kill Guilmon despite him not being evil. She starts to become friends with Renamon after Renamon nearly sacrifices herself to save her from Dokugumon, and their friendship becomes stronger when they nearly leave each other but come back together during the fight with Harpymon. By the time they traveled to the digital world, Rika was angry at the Jagamon for killing Meramon, and wished she could change Leomon's fate so Jeri wouldn't have to be sad. In the end she didn't feel like fighting anymore, but knew she had to.
Rika hated Ryo and refused to listen to reason where he was involved, but seemed to put this aside during the final battle with the D-Reaper when she didn't want to make a move that could potentially kill him.