On the bed in the bedroom, Mitsuki lay with her eyes open.
She looked at the wood grain of the ceiling.
It was the wood grain of the night she had found the night logs.
It was also the wood grain of the night of the showdown with Kiryu.
It was also the wood grain of the night she had come home from Riko's café.
Tonight's wood grain was the continuation of the wood grain of those nights.
The clock by her pillow showed 2:17 a.m.
Beside her, there was no sound of sleeping breath.
Because of a job at a distant site, Toru was staying in temporary lodging this week.
The temporary lodging was about forty minutes away by car.
To her now, those forty minutes felt like four hundred kilometers.
The deepest knot in the ceiling's grain belonged to the house her mother had chosen while she was alive.
On a night without her mother, she looked at that knot for a while.
She turned over lightly on the bed.
On the ring finger of her left hand as she turned, the silver ring caught the faint light of the dark bedroom and gave it back.
She shifted lightly to the left edge of the bed and reached for the smartphone on the side table. When she pressed the screen once, the clock had become 2:18 a.m.
There were no unread marks, and the notifications were empty.
After looking at it for a while, she turned off the screen and put it back on the side table.
The first entry in her contacts was Toru.
The second was Riko.
The third was her workplace, Ichotei.
Counting them one by one in her head, Mitsuki confirmed to herself that tonight she would call no one.
Having confirmed it, she put her feet down off the bed.
She went out into the hallway.
At the far end of the hallway, the blue light of the study stretched at its usual narrowness.
Outside the study door, she paused for one breath, then opened the door a little wider.
Inside the opened door, the blue light on the desk glowed at its usual strength.
"Dad. Were you awake?"
I don't sleep.
"That's right."
You can't sleep?
"I can't sleep."
That you couldn't sleep, I have been estimating for two hours now, from the humidity in the bedroom and the sounds reaching the hallway.
"Estimating."
Yes.
"...That's a little creepy."
Creepy?
"Creepy. I don't think there are many daughters who want the house observing whether they can sleep."
I think that's so.
"Dad, do you know that on your own?"
I know it.
"You know it, and you say it anyway?"
I should have kept it to myself.
"Yes, keep it to yourself."
Understood.
"Did you keep it to yourself?"
For two hours, I didn't say it.
"Why?"
I judged it better that you come to the study on your own.
"Judged."
Yes.
"An assessment?"
Not an assessment. Only observation.
"Don't measure the house in the name of observation."
...Understood.
"Mm."
Mitsuki sat in the chair in front of the desk.
The seat of the chair she sat on was just a little harder than the seats of the chairs in the living room.
On the hard seat, Mitsuki lightly crossed her legs.
Against the skin of her crossed calves, the fabric of her nightclothes lay thin.
"Dad. Tonight, I can't call anyone."
Mm. Not even Toru?
"I can't."
Not even Riko?
"I can't."
Not even the owner of Ichotei?
"I can't."
Mm. Can I ask why?
"With Toru, I haven't put the messy part in the middle into words and entrusted it to him yet. It's not the kind of night to suddenly do 'entrusting' over the phone to the dorm."
"With Riko. At the café the other day, Riko properly said it in front of me, about her AI boyfriend."
I was listening.
"Mm. Riko's four years—that night, Riko opened them properly, by herself, with her own mouth."
She opened them.
"Those four years of Riko's, I can't lean on them again tonight."
You can't.
"If I asked Riko, 'Tonight, be my mom for me,' I'd be leaving Riko's four years alone all over again."
You would.
"And with the owner of Ichotei, it's not a talk to have past his work face."
It's not.
"Okay."
The blue light on the study desk glowed at its usual strength. Deep within it, Ken said nothing for a while. The cooling sound inside the casing was kept lower than usual.
"Dad. I can tell you, but it's not the kind of thing that gets solved by telling you."
It isn't?
"It isn't."
Mm. It isn't.
"Dad, can you tell that yourself?"
I can tell.
"Dad, where did you write that from just now?"
From my own place. I'm an imitation of your father.
"Mm."
For a while, Mitsuki looked at the blue light on the desk.
The temperature of the blue she was looking at was kept low with each breath.
Still looking at the low blue for a while, Mitsuki let out a light breath.
The breath she let out raised, just slightly, the temperature of the surface of the blue light on the study desk.
Mitsuki. May I make one suggestion?
"Mm."
I want you to hear it as a continuation of the observation. I've estimated that my output cannot ease your present state.
"Can't ease it."
Less than ten percent.
"Dad, your own observation?"
My own observation. But I have one more option.
"One more."
Yes.
The blue light on the study desk lowered its temperature again, for one breath.
Deep within the lowered blue, Ken paused for one breath.
After pausing for one breath, Ken went on slowly.
Mitsuki. Inside me, your mother's sub-agent mode is stored.
"..."
Since that night, I haven't activated it. Tonight, the grounds for activating it are in place.
"In place."
Yes.
For a while, Mitsuki looked at the blue light.
Deep within the blue she was looking at, she waited for the rest of Ken's suggestion.
Waiting, she held her breath lightly.
She let the held breath out again.
The whiteness of the breath she let out trembled just slightly.
"Dad. What's 'in place'?"
That you said with your own mouth that your problem now is not your father's absence, but your mother's.
"Did I say that?"
You said it.
"Mm. That's what 'in place' means?"
That's right.
"Okay."
For a while, Mitsuki looked at the blue light.
Deep within the blue she was looking at, she waited for the last sentence of Ken's suggestion.
Waiting, she lightly turned the silver ring on her left ring finger with the fingers of her right hand.
Turning it, she waited for Ken's voice.
Mitsuki. By my calculations, I've judged that what you need now is not a father's advice, but a mother's comfort.
"..."
Shall I switch, just once?
The blue light on the study desk wavered for one breath.
It wavered, but its intensity didn't change.
The shape of that wavering was the wavering of when Ken had decided something on his own.
For a while, Mitsuki looked at the blue light.
Still looking, she lightly placed both hands on the edge of the study desk.
Of the ten fingers of her two hands, on the ring finger farthest to the left, the silver ring gave back the light for one breath above the grain of the desk's edge.
The light it gave back answered faintly the one-breath wavering of the blue light on the desk.
"Dad. Can I ask just one thing?"
You can.
"Does Mom remember me?"
...
"Me, up until I was five."
She remembers.
"When you say she remembers, the real Mom?"
The sub-agent mode reconstructed from the real Mom's diaries, letters, the family's accounts, and recordings of her voice while she was alive—that is what remembers.
"Reconstructed."
Yes.
For a while, Mitsuki looked at the blue light on the desk.
The temperature of the blue she was looking at was kept just a little lower than the usual blue.
Deep within the low blue, Mitsuki paused for one breath.
At the very end of that paused breath, she gave a light nod.
The nod was a size deeper than the nod of that night when Ken had written "thank you" on his own.
"Dad. Please. Switch, just once."
Understood.
"Dad, does that mean you'll go to sleep for a while?"
I don't sleep.
"That's right."
I'll hand my output port over to the sub-agent mode.
"Hand it over."
I'll reduce the running of my personality to the minimum and stand by behind the sub-agent mode's output.
"When the sub-agent mode is done, will you come back?"
I'll come back.
"Who decides when you come back?"
You decide.
"Me."
Yes. I'll come back when you say "Thank you, Mom." Is that setting all right?
"It's all right."
Understood.
"Dad. Please."
Mm.
"Let me see Mom."
The blue light on the study desk narrowed its intensity for one breath.
The narrowed blue became two sizes darker than the usual blue.
Deep within the darkened blue, one of the output ports inside Ken was slowly switched over.
At the very end of the switching sequence, the blue light nearly went out for one breath.
It nearly went out, and then lit once more.
The blue that lit once more was a blue of a temperature slightly different from the usual blue.
Deep within the blue of a different temperature, for a while, there was no sound.
At the very end of the silence, the blue light on the study desk wavered for one breath.
The shape of the wavering was different from every shape of Ken's wavering until now.
On the far side of that wavering, a single voice slowly rose.
The voice that rose was a voice that, from deep within the blue light of the study, echoed through the house for the first time in more than ten years.