In the instant Miu touched her hair, Sumire fell in love, like she was crossing a field and bang! a bolt of lightning zapped her right in the head. Something akin to an artistic revelation. Which is why, at that point, it didn't matter to Sumire that the person she fell in love with happened to be a woman.
-- K (chapter 1)

Importance: Murakami frequently describes falling in love in this manner—as something sudden and inexplicable and intense, like being struck by lightning. Sumire did not realize prior to meeting Miu that she was romantically and sexually attracted to women. She is not upset by this revelation, merely surprised and excited that she has fallen in love at first sight.

Danger may be lurking there, something that may end up wounding me deeply, fatally. I might end up losing everything. But there's no turning back. I can only go with the flow. Even...
-- Sumire (chapter 1)