Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
First Person (Central Narrator) / Young Ju Park
Think of Young Ju's narration like a diary of a really precocious, self-aware, creative little girl. (And no, not quite like The Carrie Diaries—Young Ju isn't exactly your little Miss Independent New Yorker who's all about partying and boyfriends.)
We're in her head because that's the nature of first-person, central narrators. And that's not such a bad place to be because Young Ju's really good at narrating her family's life realistically but without getting overly graphic.
Take this scene, in which Apa beats Joon:
Apa turns as if to leave and the pivots back around. He balances on one leg and swiftly kicks Joon in the stomach. Joon never saw it. Never got to prepare his body. (16.91-92)
Young Ju leaves the actual blows to our imagination while capturing that feeling of sickening surprise that comes with an unexpected hit.
What do we get as a result? A narration that's both really intimate (she gives us some majorly depressing private moments) and kind of distant, like what you might get from a peripheral narrator. That feeling of the peripheral in the voice of a central narrator is key to the light, childish tone of the book. Without it, the book's events—which, let's be honest, can get pretty uncomfortable really quickly—could become way too depressing and heavy.