Noel's actions in Calamity Trigger ended the seemingly inevitable timeloop and opened up almost infinitely new possibilites. Takamagahara intends to Intervene to choose the events that will bring it to Azure. This is the Continuum Shift.
Terumi somehow uses Sorcery to painstakingly go through all the new possibilities in this new timeline. He finds a way to take over Takamagahara.
At some point, the Imperator retrieves Nine's soul from the Boundary and puts it into an artificial human that Relius creates. This entity is called Phantom and the Imperator controls it with the Mind Eater spell. Relius, Terumi, and Izanami can give her orders.
After escaping the basement, Ragna and Noel briefly travel together and get closer. (Ragna and Jin are both perplexed by Noel because she reminds them so much of Saya.)
Jin is being extradited from Kagutsuchi in an airship, but escapes, cutting his ties with the NOL.
Kokonoe places Nu's soul into Lambda's empty body along with an IDEA Engine. She uses Lambda as a Sector Seven agent. Unknown to Kokonoe, Lambda slowly regains her memories as Nu.
Tsubaki is transferred to NOL's Zero Division (called the Wings of Justice, they focus on assassinations.) She is ordered to assassinate Jin and Noel. Tsubaki uses her family’s heirloom, Izayoi, but is very conflicted about assassinating her love interest and friend.
Relius captures Arakune. Relius tells Litchi that her best chance of helping Arakune is to join the NOL. She agrees and is given free reign to research whatever she wants, as long as Relius can see the results.
Ragna meets the Muchorin wielding Platinum and recognizes her as holding multiple souls: Luna, Sena, and Trinity. Trinity warns Ragna not to fight Terumi.
Bang meets Platinum. Trinity tips him off that his Rettenjo is important and that the NOL, not Jin, is his true enemy. Bang goes to Ikaruga to learn the truth.
Noel already has the Eye of Azure, but isn’t active as a Murakumo Unit. She’s a perfect candidate to become a Kusanagi and does not require fusion with the Azure Grimoire. Terumi captures Noel and begins the process of turning her into a Kusanagi at the Kagutsuchi Cathedral's Monolith, which functions like a Cauldron.
Jin learns about the Power of Order (which has the power to destroy Phenomenon through sheer force of will) and that he's been under the control of Yukianesa for a long time. When he tries to make his own decisions, Yukianesa won't let him draw it.
Jin encounters Tsubaki. Jin warns Tsubaki that using Izayoi will make her blind. Tsubaki begs Jin to turn himself in. Hazama activates Tsubaki's Mind Eater curse, which imposes the Imperator’s mind over Tsubaki’s mind. Jin finally uses the Power of Order to draw Yukianesa in order to try and save Tsubaki. But Tsubaki escapes.
Rachel and Hakumen transport to the Cathedral. Rachel is subdued by Terumi. Jubei enters the Cathedral and is subdued by Phantom. Hakumen is defeated by Terumi.
Ragna learns that Terumi is in the Kagutsuchi Cathedral. He finds Terumi at the Cathedral's Monolith and activates BlazBlue (his Azure Grimoire), but Terumi negates it with his own BlazBlue. Terumi reveals he's the creator of the Azure Grimoires and has a superior Grimoire to Ragna. Terumi reveals he's captured Noel and finishes activating her as a Kusanagi: Mu. He orders Mu to kill the Master Unit.
Jin and Hakumen try and fail to subdue Mu while Terumi beats up on Ragna.
Just before Terumi kills Ragna, Lambda (with all of Nu's memories restored) jumps in and takes the killing blow herself. She dies in Ragna's arm while passing Ragna her IDEA Engine. Ragna, combined with the IDEA Engine, can now bypass Terumi's negation of BlazBlue. Ragna defeats Terumi, freeing Rachel. Rachel tells Ragna the only way to stop Mu is to kill Noel.
Ragna uses the power of the Azure to bring back Noel's subdued mind/emotions/personality. This destroys his left arm in the process.
Takamagahara focus all their attention on the impossible event of Ragna freeing Noel for a brief moment, which allows Terumi to infiltrate their system and install Phantom's virus. This allows the Imperator to take control of Takamagahara.
Hazama brags about what Terumi just did. Phantom, Relius, Litchi, Tsubaki, and the Imperator appear to retreive Hazama. They leave. Jin and Ragna recognize the Imperator as the true Saya.
Kokonoe builds a mechanical left arm for Ragna. Ragna and Taokaka head to Ikaruga.
Relius and Hazuma bring Nu back to life as the "Sword of Izanami". Mu has a Life Link with Hazama and Nu has a Life Link with Ragna. This means that all these characters are semi-Immortal as long as the other is alive.