Chapter One is the first chapter of the Another manga series and also the first chapter in Period One.

The chapter starts off with little look over the town. Then, Kouichi Sakakibara is shown lying in a hospital bed at Yumigaoka Municipal Hospital, awaiting treatment for a collapsed left lung, which occurred right after arriving in Yomiyama turning 15 in the spring. His grandmother visits him, telling him that he's brave and that she feels terrible for him, before commenting abou the fact that it all happened just after he came to the town. Kouichi apologizes for all the trouble he's causing, to which his grandmother tells him to not apologize as he can't help being ill. The grandmother then tells Kouichi that she brought him a change of clothes, putting a bag of them down in the room and telling Kouichi to let her know if there's anything else he needs. As Kouichi thanks his grandmother and tells her that the doctor will give him a drainage treatment just like last year, he thinks about how today was supposed to be his first day at his new school and a day for him to make a clean start, and how it instead turned out to be the first day of the second hospital stay of his life. After Kouichi asks his grandmother about his father, the grandmother tells him that she hasn't told him about Kouichi's condition and asks Kouichi if he's in India right now, unsure of how to reach him. Kouichi reassures her, telling her that he can call him since Kouichi has his cellphone. He then thinks about how his father is a college professor and due to his work in India, Kouichi had to move to Yomoiyama to live with his grandparents and aunt without warning, concluding that Yosuke is a great researcher but a not so skilled father. The grandmother then says that despite what he does, Yosuke is a very loyal man, as he still hasn't remarried despite the amount of time since Ritsuko died.

Somewhat later Sanae Mizuno comes and wakes Kouichi up and tells him he got visitors. Two of his new classmates, namely Tomohiko Kazami and Yukari Sakuragi, has come to visit Kouichi on behalf of the class. They start to ask some weird questions like if he has live in Yomiyama before and they ends the visit with Tomohiko giving Kouichi a handshake.

Later on, Kouichi goes to the elevator and sees a strange girl with an eyepatch over her left eye and she's holding a doll. He also notices that she wears a similar school uniform as Yukari had. After the girl is ready to leave at the second basement floor, Kouichi ask why she would be there which she replies that she have to drop off something to her other half. Before the girl left, Kouichi asked after her name which she replied is Mei Misaki.

About a week later, on Kouichi's first day at school in Yomiyama, he gets a call from his dad who wonders if he's all right. Then Kouichi remembers some things that his aunt, Reiko Mikami, told him the night before. Some hours later, Kouichi is at school and gets introduced to Shoji Kubodera and Mikami-Sensei. When class starts, Kouichi introduces himself and notices a strange atmosphere in the classroom. He also notices Mei sitting in the back of the classroom. On the lunch break, Tomohiko and Naoya Teshigawara gives Kouichi a tour around the school. During the tour, Naoya asks Kouichi if he believes in ghosts, which he replies that he doesn't believe in. Tomohiko then asks if Kouichi believes in paranormal phenomena, and states not just UFO or other things like that, but with proof of actually existing. Kouichi replies that on a basic level, he wouldn't believe in it. A moment later Kouichi notices Mei sitting alone on a bench. He walks up to her and start talk to her, but she ask if he's sure with it and states that he should try to be careful as she's walking away. Then Naoya comes and tells Kouichi that they have to hurry for the gym class.

During gym class, Kouichi has a brief conversation with Yukari where she tells him that class 1 and 2 and class 4 and 5 have gym class together, whereas only class 3 is left out. Kouichi then asks about Mei but doesn't get any reply. He then notices Mei on the roof of the school building and rushes up. After Kouichi has asked some questions about her name, Mei mentions it luckily for Kouichi to not have the same first name as the attacker in Kobe. Mei then tells him that class 3 is much closer to death than the other classes and states that "it might already have started". She then leaves the roof.