"Which means it became magical recently and the most plausible explanation is," and she tilts her head towards the newspaper.

"Ssssoooo... there might be some other magical object to replace the pencil, too?"

"That's assuming the correspondence is one-to-one."

"Oh. Right. Umm..."

"We should look for other magical objects among our things," she says, and starts doing that.

None if them seem to do anything interesting if she picks them up. 

She will try scratching or lightly damaging all of her things.

As will her daughter.

This pencil takes no damage. 

...she tries tapping it against a table.

Nothing happens. 

Writing with it? Twirling it? Biting it? Putting it behind her ear?

Still nothing. 

Erasing with it? Painting with it? Scratching it, letting it fall from a height, making it stand on either end, leaving it on a table?

Nada. Seems to be one of those indestructible pencils you find lying around all the time.

Sharpening it?

The sharpener doesn't seem to work.

In the meantime Kaede tries figuring the notebook out. Can she open all pages? Write on it with anything? What happens if she reads what's already written on it out loud?

Writing has no effect. She can read previous writing all she likes. 

She tries some more stuff and eventually gives up with a sigh and closes it.

There is a sound. It's the most disturbing sound Yeong has ever heard. 

Her eyes sting, watering, as she feels pressure building in her head and smells something burning. 

"Open that again," Yeong hisses.

She does immediately.

Her head clears, the sound cuts off. 

The notebook returns to being uninteresting. 

"What happened?"