Tally Onodera is one of the Hypnos system operators, and friends with her fellow employee, Riley. Generally quite quiet, but nonetheless highly intelligent and technologically proficient, and an important part of the Hypnos machine, Tally isn’t as committed to Yamaki’s ideals as Riley is.
Tally and Riley were perpetually on-hand to announce and analyse the numerous Bio-Emergences that occurred in the early days of the Tamers’ adventures, including Guilmon, Goblinmon and Gorillamon. At one point, she and Riley talked about the mass amount of emergence that was occurring, and Riley theorised they’d soon see an unheard of level.
Several Bio-Emergences later, Yamaki planned to put his Juggernaut into action. Just prior to that, Tally and Riley picked up an erratic signal which seemed to be right under them, and Tally saw Calumon running around the room, immediately smitten by his cuteness. She tried to convince Riley of what she had seen, but Riley didn’t believe her. Later, as Tally wondered what the Juggernaut was, Riley assured it that whatever it was, it meant bad news. When the Juggernaut was activated, Tally couldn’t take the sound of screaming Digimon, begging for it to stop. Subsequently, the first Deva, Mihiramon, emerged through the vortex, and battled the Tamers, until WarGrowlmon defeated him.
When Tally and Riley detected the emergence of Sinduramon, they decided not to bother Yamaki, given the creature’s small size, but later had to call him in when it absorbed the city’s electricity.
During a brief break from their work, Riley and Tally were able to squeeze in some friendly conversation before the reappearance of Vajramon broke it up.
When Vikaralamon Bio-Emerged, the sheer size of his data almost caused Hypnos to crash, but Tally was able to shut down some non-essential programs to get the situation under control, and pre-emptively contacted the Chief Cabinet Secretary for Yamaki. In the ensuing battle between Vikaralamon and the Tamers, the Juggernaut was reactivated, but an explosion instigated by Makuramon shut it down and destroyed a substantial portion of the towers. Commenting that she knew something like this was going to happen, Tally quickly made her escape with much of the rest of the staff.
Consequently, Hypnos was shut down, and Yamaki, Riley and Tally were fired, and Yamaki saw the light, offering his aid to the Tamers before they departed for the Digital World by giving them a comm device. He and Riley were later reinstated when the unstable Juggernaut was reactivated by the head of national security, and they were able to get it under control. Tally was also reinstated, and was then seen with Riley, monitoring the disturbances the appearance of Megidramon created, quite distressed by the scale involved. Later, Tally was on hand to help corral the processing power of computers all over the planet when the Monster Makers required it to pilot the ark they had created to bring the Tamers back to Earth.
When the D-Reaper followed the Tamers back to the real world, Tally and the other Hypnos and Monster Maker members had to evacuate the Hypnos towers and operate out of a van before moving into a temporary headquarters. Tally, Riley and Yamaki went to meet the Tamers at the Matsuki bakery, then watched as the Tamers’ Digimon battled with a Pendulum Feet, one of the D-Reaper’s Agents.
After a large battle with the D-Reaper’s Agents, Tally and Janyu Wong showed Kazu and Kenta the D-Reaper’s original programming. Shortly thereafter, she, Riley and Shibumi, co-ordinated the Bio-Emergence of Grani. Later, Tally grimly reported on the D-Reaper’s spread throughout the world, and was able to open a satellite connection that allowed Yamaki to directly communicate with Takato while he and Guilmon were in battle as Gallantmon. The outcome of that battle, however, saw the D-Reaper evolve into the Mother D-Reaper, forcing the entire crew to retreat to Tsukuba, where they formulated their final plan of attack.
A week later, as the Tamers went into battle with the D-Reaper zone itself, Tally and Riley helped Yamaki and the Monster Makers coordinate Operation: Doodlebug, which devolved the D-Reaper into it’s original, harmless state.
During the events of Dimension, she continues to be an important part of Hypnos. She, along with Riley, continues to monitor the Digital World and the Biomergences. During Book Six, she retained her job during the reign of Rayleigh Thompson. In Book Seven, she escaped with Yamaki, Riley, and Eiichi to the park during the chaos after the Prime Minister's murder. The group met up with the tamers and managed to flee to the Digital World, even though Rayleigh set a trap at the park.