Many reviews here have commented on Ishiguro's unreliable narrators (let's let that classification stand, whether or not it is entirely valid or really applies to all of his work), as if this aspect of his fiction is so obvious, or that it has been so exhaustively mined, that there is little to nothing left to say about such a narrative strategy.
Christopher Banks, When We Were Orphans' narrator, is certainly unreliable, yes. But our relationship to him as an unreliable narrator is a strange one, an inverted one. I think that it's fairly clear to the reader early on that Banks's memories and perceptions do not align with those of the people with whom he surrounds himself and/or encounters. His school chums and his one-time guardian recount for him their memories of his child self as a lonely, melancholy boy, which contravene his insistent accounting of himself as a sociable, friendly, put-on-a-brave-face type of lad. His insistence, which seems to verge on a quiet, private hysteria, his disproportionate insult, and the confluence of multiple others' POV point us to the fact that the schism between how he sees himself and how the world sees/saw him is not just a matter of opinion. The novel shows us, time and again, that Christopher is unwilling, unable, to reconcile not only his memory but his ongoing lived experience (see the scene at the wedding where he is apparently subjugated to teasing and humiliation, but insists that said teasers are his friends, etc., and note that we never get to see the actual scene) to the lived experience and memory of others. (We also never get to see him work, to uncover anything, to solve anything.)
Here's where I'm sort of getting to my (excruciatingly long-winded) point...
When We Were Orphans tells us, its readers, that it is a mystery novel. The book offers us one story, the disappearance of Christopher's parents, claiming that this story is its central mystery and suggesting, by form and structure, that this will be the riddle we puzzle out as we read, alongside Christopher. Thus, we enter into a sort of contract with the book in which we agree to be careful, astute readers, who by dint of our diligence and hard work will be treated to the satisfaction of resolution.
All along, however, there is a secondary mystery that is actually the primary mystery, and that mystery is twofold: one, when will Christopher realize how deeply, irreparably damaged his perception of the world is, and two, WE THINK when we will learn the truth that his distorted vision has necessarily been hiding from us, despite our best efforts to see through it? Usually, in a novel that relies on an unreliable narrator (ignore the inherent contradiction), part of the reader's pleasure is untangling the skeins of the narrator's logic in order to arrive at some approximation of truth.
But Orphans rejects that second possibility completely. (I am in no way suggesting that this novel's project is one of relativism, in which we're meant to see that there is no objective truth, or if there is, we cannot access it.) All along the mystery/mysteries is/are just a diversion, a smokescreen, a trick (that I admire deeply and totally respect) that leads us in a circle back to what we see, finally, is an absent center. There is no mystery in the book. The truth isn't the point. There is only the fact of Christopher's mutilating orphaning, his abandonment. His grievous misapprehension of his parents' abduction/leave-taking, the emotional/psychological violence of it,and his child's need to make sense and order of the insensible strand him in mental time; he is marooned in a make-believe world in which detectives are great heroes and even celebrities, a la Sherlock Holmes--a world that history tells us did not exist as such, especially in twentieth century Britain.
When Sarah offers Christopher the chance to reject his false understanding of the world, to "see clearly," and to reject a vision of himself (one that is manufactured by an innocent egotism/narcissism that has sustained him all along) in which he is the savior not only of his parents, but also of an entire city and perhaps nation, he is, finally, unable to do so. To give that up would be to negate himself, to reject his very identity. He would be twice-orphaned.
There's a lot going on here vis a vis the orphaning, of course--colonialism and imperialism, the patronizing"helping" of the east by the west, sexual politics and power, issues of class, et al. But as I read I felt more compelled by what's "missing" in this novel than what's there.
I'll confess to being somewhat befuddled by and disappointed in the final revelation concerning Christopher's mother, and unsure about the necessity of Jennifer. My only thought about Jennifer's utility (and despite its coldness, that word seems apt) is that perhaps she's meant to enact the cycle of violence that "orphaning" perpetuates... she is orphaned twice over, and the novel's end suggests how devastating this has been for her.
When I finished the book I found myself returning to its title, over and then over again. First person narratives usually require, despite old Bobby D.'s admonition, a looking back. They are necessarily retrospective. My mind lingers on the titular "When." Despite how sad the book is, despite its ambiguous ending, the title left me feeling hopeful for Christopher in that it seems to suggest that the time of his orphaning, of Jennifer's, and even of Sarah's (sigh), is past, is gone and that, no longer orphans, having chosen to look forward, to abandon their isolation and to rely on each other, on other people they might, oh they just might... be happy.