Chise Hatori, a 15-year-old Japanese girl, was sold for five million pounds at an auction to a tall masked gentleman. Abandoned at a young age and ridiculed by her peers for her unconventional behavior, she was ready to give herself to any buyer if it meant having a place to go home to. In chains and on her way to an unknown fate, she hears whispers from robed men along her path, gossiping and complaining that such a buyer got his hands on a rare Sleigh Beggy. Ignoring the murmurs, the mysterious man leads the girl to a study, where he reveals himself to be Elias Ainsworth—a magus. After a brief confrontation and a bit of teleportation magic, the two open their eyes to Elias' picturesque cottage in rural England. Greeted by fairies and surrounded by weird and wonderful beings upon her arrival, these events mark the beginning of Chise's story as the apprentice and supposed bride of the ancient magus.

Hellsing, an organization specializing in dealing with supernatural threats, is called in to eliminate a vampire that is turning the villagers of Cheddar into ghouls. To put an end to this, the leader of the organization, Sir Integra Fairbrook Wingates Hellsing, dispatches her most formidable asset: a powerful vampire known as Alucard. Armed with only a single handgun, Alucard wreaks havoc on the monsters plaguing Cheddar. However, a young police officer, Seras Victoria, gets caught up in the chaos and becomes mortally wounded as a result. Taking pity on the girl, Alucard gives her a choice: die as a human or live on as a vampire. Seras accepts his offer and begins a new life as a member of Hellsing. Though it was her decision, Seras struggles with the fact that she is no longer human. Nevertheless, she must embrace being a creature of the night soon if she wants to survive on the front lines in the fight between humans and the supernatural.

Following the conclusion of the three-way organizational war, government bureaucrat Ango Sakaguchi recalls an event that transpired years ago, after the death of the former Port Mafia boss. Osamu Dazai, still a new recruit at the time, was tasked with investigating rumors related to a mysterious explosion that decimated part of the city years ago—and its connection to the alleged reappearance of the former boss. Due to circumstances out of his control, he is partnered with Chuuya Nakahara, the gifted yet impulsive leader of a rival clan known as the Sheep, to uncover the truth behind the case and shine a light on the myth of Arahabaki—the god of fire who might just lead Dazai to the case's solution. Meanwhile, in the present day, it is business as usual once again for the Armed Detective Agency. Their peaceful break will not last for long, however, as enemies old and new gather their strength and prepare for another face-off.

Twenty-two-year-old college dropout Tatsuhiro Satou has been a hikikomori for almost four years now. In his isolation, he has come to believe in many obscure conspiracy theories, but there is one in particular which he holds unshakable faith in: the theory that the evil conspirator behind his shut-in NEET (Not in Employment, Education or Training) status is the Nihon Hikikomori Kyokai (NHK)—an evil and secret organization dedicated to fostering the spread of hikikomori culture. NHK ni Youkoso! is a psychological dramedy that follows Tatsuhiro as he strives to escape from the NHK's wicked machinations and the disease of self-wrought isolation, while struggling to even just leave his apartment and find a job. His unexpected encounter with the mysterious Misaki Nakahara might signal a reversal of fortune for Tatsuhiro, but with this meeting comes the inevitable cost of having to face his greatest fear—society.