It's not like he hasn't noticed. He sees it. Sees how Yuzu starts acting more like a child with less responsibilities. Sees how Karin starts to accept compliments with a small smile rather than shrugging them off. Sees how she somehow becomes some kind of hybrid to his sisters: a friend, an older sister, a mother.
She becomes a lot of things for him, too, over the years: a friend, a comrade, and soon, a person that he won't live without. Can't live without.
And he doesn't know how it happens. He doesn't know how he ends up showing her that movie. That movie which his old man saw with his mother so many years ago. That boring and dark movie.
He expects her to have the same reaction as his mother. They were similar in that kind of way. They were both too empathetic for their own good. Too kind.
He expects her to cry. She does. But at the end, she smiles. She smiles as she wipes her tears.
"I want that…I want that kind of love," she whispers. To herself or him, he doesn't know. But he hears her. And really, he doesn't know how it happens. Something in him just clicks. Like he is moved back in place after being so misaligned for so long. Like he's finally opening his eyes and seeing, truly seeing, for the first time.
"Would you," he pauses as he wets his suddenly dry lips. Being in the heat for too long does that, he thinks almost in a delirious fashion. "Would you want that with me?"
And he doesn't know how it happens. But from that day, she becomes much more than what she was to him. She becomes his sun.