Disclaimer: Death Note belongs to its respective owners, none of whom are me.
She knows that there is something inherently wrong about this. A woman her age should not be doing what she is with a man - boy - his age. But she isn't a guardian to him, not a teacher, not an authority figure. To him, she is nothing.
He murmurs and lightly rubs his head into her shoulder. The sheet they hide under has ridden up just below his eyes, but she can still hear his even breathing from beneath it. His clear blue eyes flicker open, dazed but incomprehensibly calm. Incomprehensibly for him, that is. For a moment he just looks up at her, at her eyes, her nose, her lips, before he nuzzles his head into the crook of her shoulder and neck. By the time a sigh leaves him, he's already fallen back asleep.
She smiled lightly. No, to him she is nothing more than a warm embrace. One, perhaps the only one, which lets him sleep like the child he never got to be. And there is nothing wrong with that.