She seems to serve many functions at NERV, primarily the supervisor of Project E, and is first seen on the bridge when the UN gives command of the offensive to Gendo Ikari. She is pragmatic and serious, a contrast to her friend Misato Katsuragi. She was sent to collect Misato and Shinji when it appeared that Shinji would be too late in reaching the Evangelion hangar. She seems to warm to Shinji immediately, calling him by his first name and trying to make him feel more comfortable before being asked to pilot.
Ritsuko seems proud of the Eva series, and refers to Evangelion Unit 01 as a ‘she’. Despite trying to make Shinji comfortable earlier, as soon as he arrives in the hangar she becomes cooler and more analytical. Ritsuko is amazed and pleased at Shinji’s synchronisation ratio after he is inserted, and seems convinced that his piloting of the Eva could work. She seems to offer technical support to Shinji, sharing some of the command for the operation with Misato. Ritsuko is shocked when Eva 01 receives damage soon after. Ritsuko is terrified when Eva 01 reactivates and goes into berserker mode. Like Misato, she is horrified at the realisation that the angels have an AT Field. When the angel self-destructs, like everyone else on the bridge, Ritsuko seems stunned.
Misato later calls her so that Ritsuko can work through the legal paperwork to allow Shinji to live with Misato. She seems to worry that Misato would sleep with Shinji, which Misato denies.
Ritsuko is in charge of Shinji’s Eva tests, and talks to Misato briefly about Shinji’s uncle who still hasn’t called to ask after him. She is present on the bridge during the battle against the Fourth Angel. Ritsuko’s the first to realise that Toji and Kensuke’s presence in the entry plug is damaging Shinji’s ability to act.
Misato approaches Ritsuko after Shinji runs away and confides in her. Ritsuko believes they should report it, questioning if Misato thinks that she can find him by herself. When Shinji plans to leave NERV after this incident, she asks Gendo if this is alright. She mentions that there isn’t yet a Fourth Children to pilot the Eva. She suggests brainwashing Shinji, but says that his synch ratio might be affected.
While Shinji is being escorted from the Geofront, Ritsuko tells him that Gendo appreciated his efforts. When he asks after Misato, she coolly reminds him that he’s not a part of NERV anymore and she can’t tell him anything like that.
When Shinji and Misato go to the site where the Fourth Angel was defeated, Ritsuko tells him she knew he wouldn’t quit. She’s analysing data from the angel on site, and tells Misato that the angels have a 99.89% wave-form pattern to that of humans. She also tells Misato and Shinji that Commander Ikari’s hands were burnt in Eva 00’s activation test.
Later, Misato mentions that Ritsuko had forgotten to give Rei her new security pass. She is present at the reactivation test of Unit 00. After Eva 01 is hit by the Fifth Angel’s particle beam weapon, Misato asks Ritsuko to have a medic team ready. After this, Ritsuko was examining the damage to Eva 01’s armour, and theorised it would take three hours to replace. Ritsuko also felt that Eva 00 had feedback errors, meaning it couldn’t be used in a combat role against the Fifth Angel.
Ritsuko was present at the Mt Futago battle, explaining to Shinji how best to use the positron rifle and overseeing the operation alongside Misato.
Ritsuko is with Misato, Shinji and Rei watching recorded footage of Unit 02 defeating an angel at sea. She believes that the Second Children’s abilities surpass the rumours she’s heard. Ritsuko’s soon reacquainted with a college friend, Ryoji Kaji, but warns him to keep his hands to himself while Misato’s around.
While Misato is lamenting the amount of paperwork she has to go through because of the Seventh Angel fiasco, Ritsuko offers her an idea she received from Kaji that could work in defeating the twin angels. She is later seen with Misato and Kaji, discussing the lack of progress of Asuka and Shinji, as well as on the bridge in the battle against the Seventh Angel.
She is conducting tests on Rei with Gendo and the help of Maya. Although Maya has her doubts about a proposed dummy system and even voices them to Ritsuko, she believes that it is necessary to have one in the event that they need one. Ritsuko is on the bridge when the angel appears in orbit, dismissing Misato’s worries about Shinji by telling her a happy and cheerful Shinji would be more worrying.
During the NERV blackout, and in Misato’s absence, Ritsuko assumes command. She thinks that sabotage is a likely cause for the suddenness of the situation as well as the failure of the reserve generators. When Asuka and Shinji wander off into the darkness, she tells Maya to check the back-up cables.
After the power has been restored, she is talking with Misato about what happened. Thinking that someone wanted to get a layout of NERV headquarters through the power reboot, Ritsuko ran a scrambled recovery program through the Magi to feed them disinformation. She mentions that it could have been someone close to them and tells Misato that even though Kaji was elsewhere at the time, there might have been more than one enemy.
Ritsuko is present at the meeting regarding the Nevada Branch’s fate, and tells Misato that they’ve been given custody of Eva 03 in the light of the disaster. She is later seen alongside Gendo, commenting on the progress of the Dummy Plug system. She is also involved in Eva 03’s absorption into the NERV framework, responsible for finding the pilot and overseeing it’s start-up operation.
As a part of the Eva 03 absorption process she contacts the Fourth Children, Toji Suzuhara, about piloting it. She later accompanies Misato to Matsushiro and helps oversee the start-up experiment. Kaji states that Ritsuko’s injuries in the explosion during Eva 03’s start-up experiment were relatively light.
She appears at the location of the Eva 03 battle with Misato. Later, she is on the bridge during the Ninth Angel’s attack. After Rei attempts to destroy the angel with an N2 bomb, Ritsuko calls for a recovery squad to rescue her. After Eva 01 runs out of power, she runs out onto the GeoFront with Misato, Maya, Hyuga and Aoba. When Shinji achieves a 400% synch ratio with Eva 01, she murmurs that the Eva has awoken. Ritsuko is surprised when Eva 01 digests the angel’s S2 engine.
When she sees Shinji’s body has dissolved into LCL, Ritsuko mentions that it is a 400% synch ratio and that the Eva ingested Shinji. She states calmly that there is a human will at play with the Eva. With Maya she manages to come up with a plan that could rescue Shinji.
Ritsuko managed to find her mother’s research from ten years ago in order to find a way to rescue Shinji, but admits it failed then. When the procedure seems to be failing with Shinji now, she calls for all power to be cut. Shinji manages to return, but she takes no credit for it.
Shinji sees an image of Ritsuko in the Eva, trying to convince him to return.
After the salvage, Ritsuko is told to get Rei and Asuka retested as soon as possible and not concern herself with Fuyutsuki’s abduction.
Later, she is seen learning of the death of her cat from her grandmother. Ritsuko then administers a shot to Rei. She snidely comments that Rei has both Shinji and Gendo wrapped around her finger before trying to strangle her, immediately apologising and stepping back. She looks at a photo of her mother, realising that she had done the exact same thing.
She is seen monitoring Asuka’s synch test, noting that if she’s not doing well they’d have to begin restoration of Eva 00. She seems aware that something’s psychologically wrong with Asuka. Ritsuko mentions that the Fifth Children is coming soon, and gives Misato a disc to abate her suspicions. She is the first to realise that the Tenth Angel’s attack on Asuka is aimed at her mind. After the battle she explains to Shinji that Asuka’s heart and mind were too badly damaged by the attack and that has left her in a coma.
Later, Ritsuko isn’t sure exactly why Kaworu is able to synchronise with Eva 02 without the core having been rewritten. She expresses amazement at his piloting skills in the battle against the Eleventh Angel.
Ritsuko appears shocked when Rei self-destructs Eva 00 to defeat the Eleventh Angel. She doubts that Rei managed to survive the explosion, but is seemingly in charge of finding her if she did survive. She orders for the entry plug and all related parts to be destroyed. Ritsuko is seen with Rei soon after the girl is revealed to be alive, and is presented before the Committee when they seek to learn why Rei is still alive. When they reveal to her that Ikari sent her in Rei’s place, she feels used.
After her interrogation by SEELE, Ritsuko calls Shinji and offers to reveal Rei’s secrets to him. She shows them a graveyard for early Evangelions and tells Shinji that this is where his mother vanished. In Yui's place was born Rei, leading to Ritsuko revealing that the Dummy Plug’s source is Rei. In an act of destruction she destroys clones of Rei that reside in the Dummy Plug plant.
In flashbacks she reveals that she joined Gehirn in 2010, meeting Rei Ayanami earlier in 2008. She witnesses her mother strangle Rei and commit suicide. At her mothers funeral she is approached by Gendo Ikari, who claims he needs her support.
After destroying the Dummy Plug system she is held in custody, questioned by Gendo Ikari as to why she destroyed the system. She retorts that she destroyed Rei and tells him that he had no hopes for her from the start. When Misato visits her for information regarding Kaworu Nagisa, she reveals that the Second Impact was the result of an attempt to return Adam to an embryonic state before the angels awoke. She gives Misato the information she sought as well, telling her that Kaworu is the final angel.
During the invasion of NERV, Ritsuko is called out of custody in order to create systems to better defend the Magi.
She appears waiting for Gendo in Terminal Dogma near Lilith, telling him that she intends to kill him. Ritsuko attempts to use the Magi computers to kill them both. She is horrified when Magi Caspar refuses her command, and is shot down by Gendo. He tells her that he did love her.