Chapter 1 (Onisarashi-hen)
Natsumi Kimiyoshi wakes up late. On her way out the door Natsumi's grandmother, Aki Kimiyoshi draws her attention to a small altar and reminds her to worship Oyashiro before she leaves. It is revealed that Natsumi's grandmother is from Hinamizawa, and Oyashiro-sama is a matchmaking god that helped people get along with each other and get along with the demons. Her mother scolds her, saying that she will be late for school. She sets off without praying to Oyashiro-sama. On her way to school, she thinks about how Oyashiro-sama gave demons a human appearance and enabled them to coexist with humans and how the blood of humans and demons eventually mixed to give birth to the feared mountain hermits. In class, she is daydreaming about how the descendants of Oyashiro-sama still feel indebted to him and wonders if demon blood runs in her family since her grandmother is from Hinamizawa. Her best friends, Chisato and Tamako, remind her that the three of them need to go to gym class before the locker room is full. On their way out, a boy named Akira Toudou comes to retrieve his book that Chisato borrowed. While looking at Akira, Natsumi remembers that Oyashiro-sama is a matchmaking god. Akira turns out to be a childhood friend of Chisato and Tamako. After gym class, Natsumi is tasked with cleaning up. On her way to the shed, she almost falls, but Akira catches her. After helping Natsumi clean up, Akira says that he heard she likes movies and wants to know what her favorite movies and books are. Then, he asks if Natsumi would get to like him, because he likes her. He tells her that she doesn't have to answer right now and walks off. Natsumi tells him that she doesn't have a favorite movie and likes stories that have a happy endings.
On her way home, she thinks about how fortunate it was when she moved away from Okinomiya, and, upon arriving at her house, announces that she's back. Inside the house, her mother and grandmother are watching television with worried expressions. Natsumi asks what happened when an announcer on the television says that an eruption of volcanic gas occurred in Hinamizawa and its residents were all presumed dead. Natsumi's mother asks her if she remembers Hinamizawa, because it is where Grandma came from and many of their relatives live there. A few moments later, Natsumi is with her grandmother in the living room. She says that they're lucky that they moved to their current home, because they could have been in the mess. Her grandmother, however, say that it is Oyashiro-sama's curse. On the television, a reporter says that the disaster was predicted in the people of Hinamizawa's ancestral traditions. When protector god of the village unleashes his curse, miasma will be released into the air, and it will engulf and annihilate the entire village.
When the scene changes back to the living room, Natsumi asks her grandmother what Oyashiro-sama is, because she thought he was a matchmaking god. She responds by saying that he is a very important god. Then, Natsumi wonders why he committed this act. Grandma says that Oyashiro-sama is usually a very merciful god but is strict with religious precepts. She continues by saying that the Hinamizawa Disaster was caused by Oyashiro-sama's rage. The reporter is heard again saying that a similar catastrophe may have occurred a long time ago, and it remained as a legend. Natsumi says that the reporter is probably right, but her grandmother scolds her, saying that it is definitely the curse of Oyashiro-sama. She grabs her granddaughter by the wrist and takes her to the small altar shown at the beginning of the chapter. She tells Natsumi to pray with her, but Natsumi feels uncomfortable in doing so. Her grandmother pleas with her and says to do it as a favor for her grandma so she won't get cursed. She grabs her granddaughter's wrist once again, and Natsumi says that it hurts. Her grandmother pleas even more, but an afraid Natsumi replies, "NOOO!" and pushes her grandmother to the ground. Then, Natsumi's grandmother bows down and begs Oyashiro-sama not to curse Natsumi and to curse herself, instead.
The scene changes to the dinner table, and Natsumi's grandmother says that she was against moving to their current home. Natsumi's mother responds by saying that they had no choice, because her husband was promoted and transferred here. Her grandmother speaks again saying that the people of Hinamizawa cannot leave Hinamizawa, because they will be cursed if they live too far away. Natsumi's mother counters by saying that, even if she's from Hinamizawa, the rest of the family is not and no one else wants to return to that inconvenient town. Grandma speaks yet again saying that Haruko and Natsumi both have Kimiyoshi blood running through their veins and are people of Hinamizawa. Haruko responds by telling her mother that they should have left her in Okinomiya. Natsumi asks her father if Grandma was against moving here, and he says that she was, saying that she would be cursed if she did. He also says that grandma is a very religious person. Haruko and her mother are seem arguing again and Grandma exclaims that the curse of Oyashiro-sama is real. Natsumi's father tells Natsumi that Grandma is shocked by what happened to her hometown and will go back to being the Grandma they all love again soon. Natsumi, looking unconvinced, agrees. A moment later, Natsumi sees her grandmother praying to Oyashiro-sama. She says that her family won't listen to her, asks him to appease his rage, and asks him to protect her family from curses. Natsumi thinks that worshiping Oyashiro-sama is stupid.
The chapter closes by showing a fuzzy television screen with people asking Oyashiro-sama not to curse them.