Aoi arrived ten minutes before the noon they'd agreed on.
"Sorry to intrude. About how I'll be helping out—"
She stopped halfway through the sentence in the entryway, looked at Mitsuki's face, and closed her mouth. One glance seemed to tell her how little Mitsuki had slept.
"I'll make some tea. Where in the kitchen does the Professor keep his favorite tea leaves?"
"...Top right. The tin."
"Got it."
Aoi went into the kitchen. She didn't move as if she knew the place by heart, but she wasn't any more hesitant than she needed to be. Dad must have had Aoi over to the house a few times while he was alive, Mitsuki guessed. He had never brought his research home, but it seemed he hadn't kept the people from his lab away.
Aoi set two cups of tea on the table and sat down across from her.
"That thing of the Professor's," Aoi began. There was no preamble.
"Have you started it up?"
"I did. Just once."
"...How was it?"
"It had Dad's voice."
Aoi lowered her eyes to her teacup and nodded slightly.
"The Professor made that himself."
That was all Aoi said. She hesitated over whether to say more, then stroked the side of her teacup once. Her knuckles were a little rough for her age. Too much typing, probably, Mitsuki thought vaguely. Today her mouth moved a fraction more slowly when she called Dad "the Professor." Aoi was someone else walking through this house as "the house without the Professor in it," Mitsuki began to think, and then quickly took the thought back. Today, in this house, she had no room to worry about anyone else's sleeplessness.
"...It isn't something that can be made public without the family's consent. Neither the law nor funeral practice has caught up yet. So it hasn't left this house."
Aoi added this in a tone as if she were telling it to herself.
"I'll take care of the maintenance. I'll come and check on it once every six months. There's no charge."
Mitsuki kept her fingers on the rim of her teacup and lowered her eyes instead of nodding.
"Only the conversation logs. Some of them also reach the lab's server. The Professor designed it that way while he was alive."
"...Okay."
"As research, it has passed ethics review. With the Professor as his own subject. For the bereaved family—for you, Mitsuki—I'll bring the necessary documents another day. Read them, and if you don't like it, you can stop it. You can stop the transmission, or delete everything."
Aoi paused there for breath.
"There are businesses that make a trade out of this kind of thing. Imitating just the voice and the way of speaking, convincingly enough, and selling it to the people left behind. What the Professor made isn't like that. But from the outside it looks the same. So for a while, I think it's best to keep it as something just for this house."
"...Okay."
"Whether you use it or not is for you to decide, Mitsuki. The Professor said so too."
Then Aoi faltered a little. Mitsuki could tell she had started to say something and swallowed it instead.
"...Aoi."
"Yes?"
"Did Dad set something up in that thing?"
Aoi raised her eyes. Behind her glasses, they wavered for just an instant, as if searching for something. It truly was only an instant, and then Aoi quietly shook her head.
"As far as I'm aware, there's nothing special."
As far as I'm aware. Mitsuki didn't miss the qualifier.
Aoi set down her teacup and straightened her posture.
"...I can't decide today."
"No."
"I don't have to decide?"
"You don't."
Aoi stood, leaving about half of her tea in the cup.
"I'll stop by next week for the first maintenance visit. If anything troubles you before then, if you start it up, contact me anytime."
"Okay."
Aoi bowed slightly and went out the front door.
After seeing her off at the entryway, Mitsuki carried the two cups to the kitchen. She drank what Aoi had left herself. The choice of tea leaves was, for certain, Dad's taste.