For reasons unknown, Rei was inside a Phantom Field, specifically one created by Trinity Glassfille. Within this Field, which was set within the Magister's City of Ishana prior to the Dark War, Rei's memories were altered to make them believe that they were a student of the Mage's Guild. A version of Kazuma Kval was also present in this field, who was supposed to guide Rei across the island.
Rei was seemingly a transfer into the Mage's Guild. They could see a being known as the Red Sentinel - Kazuma believed this to be an indicator that Rei had tremendous magical power, despite reality being the opposite. Trinity joined in on the conversation, remarking that even Konoe A. Mercury and the Ten Sages had difficulty being able to see the Red Sentinel. Kazuma and Trinity continued working on the robes for Konoe's Canonization Ceremony, but then Rei saw the Sentinel in a hallway and gave chase. They ended up near the cauldron, which Rei recognized. The Red Sentinel began to speak, and asked that Rei not lose. Rei was then moved to a forest where they interrupted a battle against Another Dark Mai and Ciel Sulfur. Mai took notice and went to kill Rei, but at that moment, Phenomenon Intervention occurred. Mai was distracted, so Ciel took Rei away from the fight.
Rei lost consciousness. They began to dream, seeing Ciel, who introduced herself and promised to protect them. Rei awoke, finding Ciel next to them. Kazuma ran over to the both of them, asking where Rei had been, and becoming increasingly alarmed as monsters began to swarm around the trio. Rei stood back, as they are unable to fight, while both Ciel and Kazuma fought against the surrounding beasts. As the battle ended, Ciel called out to Rei, referring to them as an Observer.
Moments later Another Dark Mai arrived. Rei appeared to recognize her, but did not know where from. Kazuma and Ciel's noisy conversation about whether to engage against Mai lead to her turning her attention towards them. Mai did not take well to being called an enemy, and introduced herself as a "villain" who was going to stab Rei again and again. Rei then began to slightly break down, but was shaken out of it by Ciel, who asked that they don't Observe Another Dark Mai too closely. Mai then threatened to kill them all again, but the trio were teleported away from her thanks to Raabe, who had used Phenomenon Intervention. Both Rei and Kazuma were shocked by this, but Ciel explained the situation to them both now that they were safe. Ciel continued, telling them both that she belonged to the Mitsurugi Agency, and was not native to Ishana. Together the group decided that, since this Ishana was essentially empty of people, they would try to find the cauldron within Ishana and find a way to solve what was wrong with the island.
As the group headed further into the island, Kazuma explained to Rei about the Mage's Guild and Ishana's history. It was also here that Kazuma pointed out that Rei's uniform was an old design, one that hadn't been used by the Guild in a long time, and that Rei also seemed incapable of using either magic or sorcery. They were then attacked by monsters, but they were fought off due to a combination from Ciel and Rei which they discovered together, allowing them summon Chrono Phantasma (Those Who Should Not Exist) as embodied units to fight alongside themselves. The group then decided to head north-east towards an Ishanan port to find a communications device in order to see who else might be on the island. When they eventually arrived, they did not find a working device, but instead were met by a piercing scream in the distance. Rei went to run over with Kazuma, but was held by by Ciel. Rei explained that they couldn't just sit back and let someone get hurt. Rei convinced Ciel to come with them.
The group then fought through waves of monsters, with Rei using summoned units to help. They finally made their way through, finding Trinity Glassfille. She told them that Ishana's barrier had disappeared and that a secondary defence system had likely activated in order to isolate the island within another dimension. The group decided that the Great Library was likely the one place that would have information on how to save Ishana from its predicament. On Trinity's suggestion, the group went through the sewers to reach the library while avoiding detection, but were attacked by more monsters. When they made their way out of the sewers and into a park, they were attacked again. The island was swarming with monsters that were attracted to Ciel and seemingly Rei as well. The monsters were defeated and the group made their way further towards the library, walking past the Grand Clock. Rei noticed that the time on it had not changed, yet to Trinity, the time was indeed different.
Finally inside the Great Library, Trinity made it clear that they were going to have to fight a security system in order to enter a forbidden section of the library which would contain information they were looking for. After beating the golems summoned by the system, Trinity told them that she was uncomfortable with Ciel entering since she is an outsider, but Ciel stood firm, telling her that she needed to enter in order to protect Rei. Rei and Kazuma reaffirmed their trust in her, eventually persuading Trinity to allow both Ciel and Raabe access to the hallowed sections. Rei helped comb through the numerous books, but it was Ciel who suggested that they find the cauldron once more and deactivate it, thereby taking Ishana out of the secondary security which had placed it within another dimension. Before proceeding, Rei was asked if this plan was okay and they gave it the go ahead. The team then left, making their way to the most sacred of Ishana's destinations where the cauldron likely lay - the Ishana Cathedral.
On their way to the cathedral, Ciel confessed that she was going to destroy the cauldron. Trinity and Kazuma couldn't accept this, but Rei told them that they had no reason to distrust her, eventually persuading both of them that the plan was sound. As they descended through the cathedral towards the cauldron, both Ciel and Kazuma told Trinity that they believed her to be an Observer who had subconsciously recreated Ishana, but they were unable to figure out why Rei had been placed within the Phantom Field alongside Kazuma. More monsters flooded in that the group defeated.
As the group reached the cauldron, they saw Another Dark Mai, who had been waiting for their arrival. She expressed an interest in Rei and Ciel, telling them that she had stayed within the Field because she found them interesting. A battle begun between Dark Mai and the units summoned by Rei and Ciel. Eventually, the dust settled and Dark Mai left via the cauldron. Trinity then turned to the group, unable to accept her position as an Observer and unable to let her desires go. She was battled and defeated. Ciel was then able to activate her BlazBlue Alternative as Rei Observed it, allowing for the cauldron to be destroyed and Trinity to be freed from her Phantom Field. As the Field was beginning to reform into a new Possibility, Ciel took Rei with her and the two came on board of the Dimensional Boundary Submersible Warship Fugaku. When Rei gained an understanding of where they were, they were greeted by Kagami Hajou.
- BlazBlue Alternative: Dark War, Prologue, 1
- BlazBlue Alternative: Dark War, Prologue, 2
- BlazBlue Alternative: Dark War, Prologue, 3 - 1
- BlazBlue Alternative: Dark War, Prologue, 3 - 2
- BlazBlue Alternative: Dark War, Prologue, 3 - 4
- BlazBlue Alternative: Dark War, Prologue, 4 - 1
- BlazBlue Alternative: Dark War, Prologue, 4 - 2
- BlazBlue Alternative: Dark War, Prologue 5 - 1
- BlazBlue Alternative: Dark War, Prologue 5 - 2
- BlazBlue Alternative: Dark War, Prologue 5 - 3
- BlazBlue Alternative: Dark War, Prologue 6 - 1
- BlazBlue Alternative: Dark War, Prologue 6 - 2
- BlazBlue Alternative: Dark War, Prologue 7 - 1
- BlazBlue Alternative: Dark War, Prologue 7 - 2
- BlazBlue Alternative: Dark War, Prologue 7 - 3