In Shusaku Endo's When I Whistle, the literary device that most stands out is the author's use of flashback.
Flashback is when the author turns the attention of the reader to a time in the past which has had some effect on the present-day characters and/or events taking place at present. eNotes defines "flashback" as...
In general, flashback offers the reader information that occurred in the past, prior to the onset of the story—the information is essential in understanding the setting, plot and characters of the present, and how they develop.
"Character flashback" provides information about a character's past. It is used to "create suspense...or, develop a character."
eNotes summarizes how the author manipulates the plot between past and present:
[The] brief conversation provokes an extended reminiscence that transports Ozu back to a simpler, more serene time in his life.
The story opens as Ozu is reading Madame Bovary on the bullet train. The opening of Gustave Flaubert's novel is very similar to the day Ozu first met his friend Flatfish. First Ozu reads the beginning segment from his novel, and then he recalls how similar it was when he met Flatfish. He describes it all as follows:
'While we were in the study hall, the headmaster came in, accompanied by a new student and a custodian carrying a big desk...We couldn't see him well for the door, but the new student was a country boy of about fifteen...'
Flaubert's novel Madame Bovary begins with this scene. This afternoon on the bullet train, as Ozu rewound the film of his memory, the scene that slowly floated up like a bubble of water...was also a day when a new student had been brought into the classroom...
This is only the first instance of using flashback to tell of Ozu's past, and to remember a simpler more innocent time—for Ozu and perhaps even for his country. The action or structure of the story takes Ozu back to the innocence of his childhood, and then flips forward again to describe his life—not a glamorous or fulfilling one—and his struggles with his son, Eiichi, who is living in a world much different than the one Ozu grew up in.
Flashback allows the author to give important information about Ozu by describing his past—in sharp contrast to the life he has as an adult, especially with regard to his relationship with his son.