Tsumihoroboshi-hen

Atonement Chapter (罪滅し編) is the sixth arc in the series and the second of. It is told from the perspectives of Keiichi Maebara and Rena Ryuuguu and explores Rena's relationship with her father as well as the Hinamizawa Syndrome. The corresponding question arc is.

Plot
Tsumihoroboshi-hen opens with a scene at the garbage dump with Rena Ryuuguu being confronted by Keiichi Maebara, Mion Sonozaki, Satoko Houjou, and Rika Furude for reasons unknown. Rena then launches into a confession. She reveals through flashback that her high-flying mother cheated on Rena's father with a man named Akihito. The affair led to a pregnancy which led to Rena's mother divorcing Rena's father. Rena, angered at her mother's betrayal, chose to stay with her father. Rena was visited by Oyashiro-sama and was urged to return to Hinamizawa, which the family had originally moved away from to further Rena's mother's career. Rena, believing the Oyashiro-sama cursed the Ryuuguu family for leaving Hinamizawa, forms a deep belief in Oyashiro-sama.

After the pair return to Hinamizawa, Rena's father eventually falls in love with another woman, Rina Mamiya. While in a coffeehouse, Rena overhears an exchange revealing that Rina is actually a con artist named Ritsuko who is playing a badger game on Rena's father. In retaliation, Rena lures Ritsuko to a secret spot deep within the nearby garbage dump and beats her to death with a lead pipe. The following day, Ritsuko's partner in crime, Teppei Houjou, comes to the Ryuuguu house as part of the badger game. He begins yelling and confronts Rena's father with a fake marriage certificate suggesting that Rena's father impregnated his wife, which Teppei would then use as blackmail to extort money from Rena's father. After the confrontation, Rena tells Teppei that Ritsuko has something to tell him and has Teppei follow her to the garbage dump where she turns on Teppei and splits his forehead with an axe.

Rena spends a number of days dismembering the bodies and deciding where to hide them. One day, she skips club activity to go to the garbage dump and continue her work. Coincidentally, that is the day that the club decided to play mahjongg only to learn that they didn't have all the tiles because Mion hid some with the intention of cheating. Instead, the club decides to go treasure hunting in the garbage dump as they knew Rena enjoyed doing. Then the story is brought back to the opening scene. At this point, everyone forgives Rena for what she has done and helps her hide the body parts deep in the mountain forests.

Several days pass and Rena meets Miyo Takano in the Okinomiya library. Miyo gives Rena a collection of scrapbooks she has assembled detailing her research into Hinamizawa's past. A few days later, after the Watanagashi Festival, Rena learns from detective Kuraudo Ooishi that Miyo and her friend Jirou Tomitake were killed. Rena becomes frightened when she learns that Jirou died by clawing out his throat, which Rena relates to a psychotic experience she had following her parents' divorce when she began to cut and exsanguinate herself to rid her blood of what she believes are maggots. Rena believes that Jirou clawed out his throat in attempt to rid himself of maggots, a belief strengthened by the conspiracy theories laid out in Miyo's scrapbooks. Rena shares the details of Miyo's theories with Keiichi, believing him to be one of the only people she could trust with the information. Although he believes her at first, Keiichi dismisses Rena's stories after having a conversation about them with Mion.

Rena increasingly believes that a group of religious fanatics are attempting to kill her and misconstrues several experiences to fit that narrative. Her paranoia eventually leads Rena to steal cash from her father's safe and run away from home to hide in her getaway in the garbage dump. Eventually, Rena confides in Ooishi her conspiracy theories and requests that Ooishi do her best to help her. This leads the police to search the entirety of Hinamizawa looking for Rena, believing that the Sonozaki family is responsible for driving her away. When she sees the police searching for Rena, Mion comes to the conclusion that they are searching for her in order to bring her in as a material witness to the death of Ritsuko and Teppei which leads Mion to convince the Sonozaki family to search for Rena and protect her from the police. Eventually, the Sonozaki family and the police force meet and clear up the misunderstanding while joining forces to find Rena.

Keiichi finds Rena and desperately tries to convince Rena that Miyo's theories are baseless, claiming that she should believe him since he is her friend. Keiichi is strongly driven by a memory he discovers from wherein he beat Rena and Mion to death despite them only trying to help him and wants to save Rena from committing the same sin. Despite this, Rena becomes consumed by Miyo's theory that a bioterrorism attack on Hinamizawa is imminent and struggles to find people in authority who believe her. In an attempt to force the police to see her story, Rena emerges from hiding and takes everyone in school hostage and threatens to blow up the classroom with gasoline unless the police comply with her demands by 7PM, by which time a kitchen timer will ignite the classroom regardless.. Keiichi, Rika, and Satoko manage to distract Rika and get her to leave the classroom, allowing Keiichi to run to the roof of the school and disarm the kitchen timer before turning around and having a face-off with Rena on the roof. The fight between the two lasts roughly ten minutes before they call it a draw. Rena, by the time the fight is over, has realized Keiichi's point of view and broken free from her apparently psychotic state.

Villagers

 * Rena Ryuuguu
 * Keiichi Maebara
 * Mion Sonozaki
 * Shion Sonozaki
 * Rika Furude
 * Satoko Houjou
 * Teppei Houjou

Outsiders

 * Ritsuko Mamiya
 * Kuraudo Ooishi
 * Miyo Takano
 * Jirou Tomitake
 * Tatsuyoshi Kasai

Mentioned

 * Oyashiro-sama
 * Oryou Sonozaki
 * Kiichirou Kimiyoshi
 * Mr. Ryuuguu
 * Mrs. Ryuuguu
 * Akihito

Deaths and Disappearances
All deaths and disappearances are listed only as they are told in  and apply only for the individual arc, not the overall series.

Deaths

 * Ritsuko Mamiya, beaten with a lead pipe and falls down a mountain of junk, breaking her neck.
 * Teppei Houjou, has his forehead split with an axe.
 * Jirou Tomitake, died of blood loss after clawing out his own throat June 19, 1983 on the night of the Watanagashi.
 * Miyo Takano, strangled and burned in an oil drum in the Gifu Mountains June 19, 1983 on the night of the Watanagashi.
 * Rika Furude, brutally murdered June 25, 1983.
 * Kyousuke Irie, committed suicide June 26, 1983 immediately prior to the Great Hinamizawa Disaster.
 * Everyone in Hinamizawa not listed otherwise, died June 26, 1983 of gas poisoning during Great Hinamizawa Disaster.
 * Some people who used to live in Hinamizawa, started showing erratic behavior right after Great Hinamizawa Disaster. Some died mysteriously in hospitals, while others started dying in other strange ways.

Disappearances

 * Satoshi Houjou, disappeared June 1982, one year before the story.

Trivia

 *  never converges with its corresponding question arc,, as did with.
 *  is the first arc wherein the characters show awareness of parallel worlds.
 * While in the garbage dump, Keiichi repeatedly references a "memory that shouldn't exist" from a "what-if world" wherein he deprived many of life to save one of his friends. The world he is referring to is the world of.
 * Ooishi claims that "no matter what path [he] chooses...Tomitake Jirou always dies".
 * Rika says she'd like to inject Rena with her syringe by force but "it never really works", likely in reference to her failed attempt to drug Shion in.
 * Keiichi actually has a direct flashback to many events in in an attempt to rationalize everyone's behavior though he acknowledges those memories as coming from a "nonexistent, different world".
 * Rika claims that Keiichi's remembrance of events from another world is a "miracle", possibly hinting towards Rika's affiliation with Bernkastel, the Witch of Miracles, in.