[3] Onda's writing style is classified as shin honkaku, a "new orthodox" form of Japanese detective fiction, and is structured to focus on three converging timelines.

As they celebrate a multi-generational birthday party, that admiration is sullied when an unnamed man presents the attendants with sake and soft drinks as a gift.

In a perspective change, the unnamed narrator interviews someone who was a kid at the time of the murders and was friendly with the young man to the point of calling him "Big Brother".

The man called Big Brother delivered the drink but had no motive to kill, and Hisako Aosawa witnessed the entirety of the poisoning but cannot give any tangible details.

[11] Decades later there is still a search for the truth among long-held beliefs and the sour feelings of the people living in the seaside city of K—.

[2] Onda uses a framing device, a significant element to ground the story at the beginning or end of a work, in the form of a poem called Eugenia, a reference to the Japanese publication title.

Albeit mostly similar, shin honkaku has looser genre boundaries and can include less formal literary devices.

The justification for her decision came from Ken'ichi Sakemi who made his successful debut as a writer at age 25, only a year older than Onda.

Drawing inspiration from Michel Petrucciani's song "Eugenia," Onda wrote a poem by the same name which helps frame the story of life and death seen in The Aosawa Murders.

[5] The mass poisoning case in The Aosawa Murders references a crime that was committed in Japan known as the Teigin Incident.

On January 26, 1948, twelve people died after a man disguised as a public health official entered a bank and urged the employees to ingest an immunization for the recent dysentery outbreak.

Hirasawa was eventually sentenced to execution by hanging though he pursued exoneration for 40 years before he died in prison at age 95.

[8] Jennifer Reese in The New York Times "What to Read" shortlist published February 20, 2020 praises Riku Onda for her engrossing, complex story.

[2] Tara Cheesman in the Los Angeles Review of Books of March 25, 2020 tells of Onda's work as a locked-room puzzle, interwoven with a one-sided interview style and a nonlinear plot-line.

[4] Jill Dobson in The Japan Society review summarizes Onda's intended effect of the novel: the revelation of a crime is oftentimes messy, and the story itself meanders.

[11] Terry Hong in Smithsonian BookDragon (January 2020) compliments Onda's unique style of clues that address both the motive and perpetrator of a crime, engaging readers in a hunt for the truth.