Case File Synopsis
Date was restrained to the Psync machine when he woke up. Aiba's body was shorted out from the taser's shock, and only her communication function was still working. Then, a man entered: Saito, who was in #89's body...
Saito claimed that Hitomi and Iris were still alive, because he wanted to kill them in front of Date after switching bodies. Date, barely containing his anger, questioned Saito about the past six days and the incident 18 years ago. After finishing his story, Saito kicked his plan into motion and knocked out Date to begin the Psync.
Dark Room, Kabasaki Chemical Plant, Wednesday 12:55 AM
Date woke up restrained to the Prototype Psync Machine. Aiba's motor functions had been short-circuited by the taser, so she was unable to leave Date's eye to free him. Aiba's attempted to reach ABIS for support had been ignored, likely as a result of So Sejima's influence. Eventually, Saito Sejima (in #89's body) entered the room and sat down to talk to him. Date figured out that Saito had been in Renju's body until recently. Saito speculated that Date knew about the Psync Machine's ability to swap bodies because he was regaining his memories. Date also knew that his body was originally Saito's, and #89's body was originally his.
Saito demanded his body back. He explained that Iris and Hitomi were still alive, but he planned to kill them after taking back his original body. Saito wanted to wait before killing them (in front of Date) because of the release of dopamine and endorphins he would get from his own brain. Saito decided he wanted to see Date mad before beginning the Psync, and went over his crimes from the last week.
On Friday, Saito used Shoko's body to call Renju to the chemical plant and swap bodies. As Renju, he stabbed Shoko's body to death, then took the body to Bloom Park. As Saito explained, Date realized he already knew, as if he had heard it before. Saito confirmed that he had thrown Shoko's rental phone into the horse himself. The phone fell out of her clothes while he tied her to the horse, so he put it in the horse to dispose of it.
On Saturday, as Renju, Saito targeted Iris. He called her to Sunfish Pocket around 5:00 PM, but she refused to come. Aiba realized it was because Date had seen Manaka's body in Mizuki's Somnium, mistaken her for Iris, and called her to tell her not to go anywhere, at 4:52 PM. Saito thought Iris might trust him if he arrived in person, so he drove Renju's car to pick her up. However, at 6:10 PM, he got in a car accident on the highway and lost consciousness.
On Sunday, Saito woke up in the hospital after his surgery. It was successful, but Renju's organs had not completely healed. Still determined to carry out his plan, Saito escaped the hospital, rented a car, and headed for the Sagan Residence. He arrived at 2:00 AM and asked Iris to come with him to the chemical plant. She agreed, but Saito's sleeping pills had been left behind in Renju's car, so he had to hope she would not try to run. When he tried to take her inside, Iris got scared and ran away. Unable to chase her because of Renju's injuries, Saito collapsed.
On Monday, Saito woke up around noon in the chemical plant. He got a call from Pewter, who he asked to let #89 escape police custody. Pewter agreed, and Saito arrived to pick #89 up. He knew Iris would trust him in #89's body, and he wanted himself and Date to get their original bodies back before he killed Iris and Hitomi. Saito took Rohan (in #89's body) to the chemical plant. Saito put him to sleep and began the Psync. Rohan then died from Renju's injuries. Saito also confirmed that he hired the mercenaries with Renju's money, and left Pewter in charge of them.
On Tuesday, Saito made a video call to Iris at 1:40 AM. He told her he wanted to see her, and Iris got excited and dropped her guard. She agreed to meet up, and Saito put her to sleep in the car, restrained her, and called Hitomi. Aiba realized that Iris's "most trusted person" from her note was actually Date.
Saito explained that 18 years ago, he heard So on the phone talking about going to see Manaka. He followed him in a taxi to the Harbor Warehouse District, where he hid until Manaka turned to leave, then stabbed her. Before killing Manaka, Saito explained that he would kill cats and pigeons to feel happiness. However, he eventually grew a tolerance to it, and decided to try killing a human. He saw Manaka as someone who had stolen his father's affection from him, and decided to make her his target. Saito wondered if things would be different if he never killed Manaka.
After explaining everything, Saito decided he was done waiting. Saito put Date to sleep and took Aiba out of his left eye socket. He then ripped his own left eye out, and began the Psync.
- The name sousAI (相殺) translates to "Offset" or "Counterbalance," which is in reference to Kaname Date and Saito Sejima, who are not only parallels of one another as characters, but are also presently inhabiting the other person's body, to which Saito is attempting to return and balance to its proper position.