Notes: Written for dn_contest's "fight" prompt. Thanks to vashti, as usual, for first reader duties.
Belief
Sachiko can remember Light and Sayu fighting only once.
Sayu was five, and she'd already eaten all of her New Year's candy. She climbed up on the couch, where Light was reading. "Big brother, I want some mochi."
"Then you should have saved it like I did," Light said, with a little smile.
"But now you have it all and I don't have any."
Light turned a page. "We started with the same amount of candy, Sayu."
His calm seemed to annoy her. "You should be nicer to me, big brother."
Light's expression didn't change, but he set the book aside. "I am nice to you. Who fixed your kite when it was torn?"
"You did," Sayu admitted, still pouting. "But that was ages ago."
"It was two weeks ago."
"Shut up, Light, you're such a know-it-all."
Sachiko glanced up from the thank-you letter she was writing to see if this called for motherly intervention yet, but Light looked more disappointed than angry.
"You should be nicer, little sister," he said, mildly.
"Don't tell me what to do!" She got up and stomped out of the room. Light looked over at Sachiko, gave a little shrug, and picked his book up again.
It wasn't long before Sayu came back, mouth set in a determined line, carrying an unopened package of strawberry mochi.
Light reacted before Sachiko could frame a suitably stern response to this brazen theft. (Truth be told, she was secretly amused.)
"Sayu, those are mine. Stop being a brat."
"You're a brat!"
"Give it back."
"No! You're mean. You don't even want it!"
"Sayu," Sachiko said warningly.
"It's all right, mom," Light said. The anger had drained out of him, and he looked as composed as ever. "You can have it, Sayu."
Sayu glared at him a moment longer, then left with her prize.
"That was nice of you, Light," Sachiko said.
"It wasn't worth fighting over."
The next day, when Sachiko went shopping, she bought two new packages of mochi. She thought, standing in the checkout line, that she shouldn't reward Light for rewarding Sayu's bad behavior, but in the next moment, she felt he couldn't have been expected to understand that, and deserved it more than ever, for having been kind enough to give his little sister what she wanted.
She gave the candy to Light, and he looked up at her with a strangely adult expression, as if he had expected this. He was like that sometimes, so solemn for an eight-year-old. It gave nearly everything he said or did a grown-up gravity. "Thank you, mother."
Sachiko still doesn't know if Light ever ate that mochi. She doesn't know, either, why she thinks of that now, watching Light sit by his sister's bed. He holds her hand and speaks quietly to her, but Sachiko can hear his words.
"I'll make sure Mello pays for this, Sayu, even if I have to take justice into my own hands. Even if it brings me to Kira's attention." He looks more grim than Sachiko can remember seeing him, and she wants to say, Light, don't talk that way, but the memory of the New Year's candy is still with her, and she thinks, He'd say this is worth a fight.
She doesn't know what demon of distrust makes her wonder, the thought acknowledged and banished in the same instant, But for whose benefit is this, really?
Of course Light wants to reassure Sayu that she'll get better, that her suffering will be avenged. He's their light in more than just name, Sachiko's brilliant and beautiful boy, and if she was never sure exactly how to do the best for him, that was only because he was too smart, too thoughtful.
Her whole family, now, is tangled up in the Kira case, and Sachiko wonders sometimes if there was something she could have done, once upon a time, to keep it from coming to this. It's silly of her, she tells herself, as Light kisses Sayu's forehead like he's giving her a blessing, like he's sealing a promise. She couldn't love Soichiro and Light so if they were other than what they are.
Light gives her a bright smile that she wants to believe he doesn't have to fake. "Don't worry, mom. I know it's hard to believe right now, but it'll all work out for the best in the end."