WARNING: The following contains spoilers for Episode 5 of Mars Red, now streaming on Funimation.
Episode 5 of Mars Red, "Persona Non-Grata," starts directly after the events of Episode 4, in which the four Code Zero vampires investigated the mysterious deaths of recently turned vampires -- some of them had been poisoned, and some drained by different bloodsuckers. At the end of Episode 4, a mob of mindless vampires attacked Code Zero, but Shutaru used his superior combat skills to cut them down by the dozen, surprising and horrifying Maeda, his superior, who collapsed from shock, pain, and exhaustion.
Episode 4 implied that the people responsible for the Red Light District outbreak were Rufus Glenn, a Scottish vampire who pretended to be a British parfumier/whisky importer to move blood vials contaminated with a corrupt version of the vampire virus, and Okimura, General Nakajima's seemingly affable superior. However, Episode 5 shows that the truth is much more convoluted.
Rufus Glenn is a Double Agent
As it turns out, Rufus Glenn isn't actually a high-ranking member of British vampire society, but a mere butler to S-Class vampires. These vampires are soft-spoken and polite, but cold, cruel and incredibly bloodthirsty. They came with Rufus to Tokyo with the intent of taking over the city and feeding on its citizens. In fact, one of Rufus' superiors slaughters a young man so thoroughly that her pristine Victorian dress ends up splattered with blood.
For the British vampires, Rufus Glenn is just a useful servant who also happened to invent Ascra, a supposedly safe artificial blood. He was meant to keep them in utmost comfort and make sure that the zombie vampires they brought to sell to the Japanese government remained under lock and key. Instead, Rufus poisoned the Ascra he fed his overladies and let the zombie vampires roam the streets.
Okimura's British Connection
This leads us to Mars Red's Okimura, the government official who was in contact with Rufus Glenn, welcoming him to Tokyo and organizing his perfume showcase at the Frank Lloyd Wright Imperial Hotel. Okimura isn't top brass, but a bureaucrat in charge of liaising for General Nakajima, who championed the creation of a secret Japanese force of vampire soldiers, and the rest of the army. Up to this point, he had acted as Nakajima's ally, smoothing the waters when he asked for more time to develop his long-term project, but in this episode, he eliminates the budget allocated to Code Zero.
At the same time, Okimura informs Nakajima that he had finalized negotiations to bring fully trained S-Class mercenary vampires from Great Britain to serve Japanese interests; Nakajima's life project was no longer necessary, and he should incinerate his assets (and by assets, Okimura means the four vampires of Code Zero). And, given his connection with Glenn, it is very possible that Okimura's had a hand in the Red Light District's vampiric outbreak.
However, Okimura's plans were never going to succeed. The vampires he "bought" didn't intend to abide by his rules, but to take on as much power as they could to feed on a terrified population. Regardless of his intentions, Okimura effectively sold out his own people, and if Rufus Glenn had not poisoned these vampires -- his superiors and Okimura's on-paper allies -- Okimura would have become a dishonored traitor.
General Nakajima's Secret Project
Okimura's betrayal in Mars Red seemed a bit over the top; while he insisted that Nakajima's project cost too much, any viewer of the show would have to wonder why, exactly. The four vampires were self-sufficient, lived in a pre-existing underground bunker, were working without any pay and their headquarters were in the space behind a massive clock, with no frills at all. Even accounting for Takeuchi's scientific equipment, the budget line could not be as high as Okimura made it seem.
Unless... Code Zero was just a cover for the real project, Nakajima's main mission: training an entire battalion of vampiric supersoldiers that only existed for war and would be loyal only to him, with no minds of their own. General Nakajima had used the four vampires of Code Zero to distract his enemies and make them think that his plan of creating vampire soldiers was failing spectacularly. In reality, he had trained exceedingly intimidating, strong and obedient vampire special forces on the side.
Fortunately, Nakajima deploys his super vampire soldiers to stop the second zombie vampire outbreak, not to smash them down to pieces. That doesn't ease the bad feeling the Code Zero lads have about the whole situation. Nakajima then kills Okimura for betraying him.