“Mogi and I have already made up our minds on this. Aizawa, Matsuda, if you wish to continue working on this case, you'll have to hand in your letter of resignation to the NPA just as Mogi and I are going to do. Like it or not, you cannot pursue Kira as a member of the police force any more.”
Ally (仲間, Nakama) is the eighteenth episode of the Death Note anime series.
In the morning, Aizawa arrives at the Task Force's new building, where he is forced to go through a lengthy security system (even stripping off his pants) just to get inside. When he finally arrives, Soichiro notices a bandage on his head, and Aizawa says that he had a bit of a fight with his wife over how much he has had to work.
The two and Matsuda watch the surveillance in Misa's room, where a lethargic L eats a cake and Light and Misa just sit around. Misa tries to push L into getting some privacy for the "date," but L says otherwise and takes Misa's cake. Light questions why L is not motivated at all, and L says it's because he is depressed that Light is not Kira and his deduction was wrong. However, he does think that Misa and Light were Kira until some moment in their confinement and that the new Kira was controlling their actions. L concludes that Kira's power passes from person to person, making trying to catch him futile. Frustrated that L is simply giving up because he isn't satisfied that Light and Misa cannot be conclusively said to be the Kiras, Light punches him in the face, causing them both to fly into the wall and knock over a plant. L promptly kicks Light in the face, knocking over a couch, while Misa looks on in shock as they continue fighting. Matsuda eventually breaks up the fight by distracting them with an article about Misa, only to overhear them say that he is acting stupid again.
Light later goes through Kira killings when he notices some that are all CEOs of big companies, resulting in a downturn in their company's stock with the sole exception of Yotsuba. Light concludes that Kira is supporting Yotsuba. Building on this, L suggests that Kira killing criminals is a diversion to raise Yotsuba's stakes. Meanwhile, at Yotsuba itself, the eight people from the previous episode discuss their three most recent killings. One of them, Hatori, questions why they all died of heart attacks, and it is explained that it was done because one was on vacation, lessening the otherwise inevitable suspicion.
Matsuda and Aizawa inform Soichiro and Mogi of Light's discovery, but Soichiro seems rather despondent on it. He then reveals that many politicians have been bribed by Kira: if anyone from the police tries to stop Kira, they will die. This leaves them with a dilemma: they can either quit their jobs and pursue the Kira case entirely before retiring (Soichiro and Mogi's choice), keep both and risk getting fired, or go back to the NPA permanently. L suggests that they go back to the NPA, since he can solve the case on his own with Light, and they won't have enough info that they otherwise would if they were police officers. He ultimately leaves the choice to them. While Soichiro and Mogi remain adamant, Matsuda decides to join them. However, Aizawa is let struggling; he needs the money but doesn't want to ruin Ukita's memory. At that moment, Watari phones in and notes that L had made it such that if Task Force members were to lose their jobs, their financial status will be accompanied by L. Although Matsuda thinks this will convince Aizawa to stay, instead it makes him furious, as he realizes L was just testing their loyalty and still doesn't trust them. Declaring he hates L, he storms out, quitting the Task Force.
As Yotsuba's deaths pile up, Soichiro notices that all of their recent deaths are centered during the weekends, specifically around Friday night and Saturday afternoon, so the group decides to center their focus there. Mogi then gathers documents on all 300,000 of Yotsuba's employees. Seeing how he has nothing to contribute, Matsuda stands up and asks L if can do anything beyond be Misa's manager; L ends up asking him for coffee, much to Matsuda's dismay. L also asks for coffee for two "guests," whom L announces are two new members to the investigation team. They happen to be a con man named Aiber and a thief-by-trade named Wedy, whom L plans to have go undercover (the former as a spy, the latter to break into facilities) when the need arises. The others question stooping so low, but L deems it is necessary, and since Aiber and Wedy are incredibly low on the radar, they can't be killed by Kira.
Meanwhile, Aizawa is sitting in a park when his wife and daughter coincidentally pass him. He tells them he has gotten some leave, and overcome with emotion in the knowledge he can always be with his family, breaks down in tears, while his family looks on in confusion.