The next day after my imouto increased to three―

I went to the hamburger shop near the junior college where Aya attends.

「I'm sorry to keep you waiting, onii-san.」

「Ossu, onii-chan~.」

Mai-san has something to discuss and sets up a meeting.

However, although Mai-san is calling me『onii-san』......

should I propose『become my imouto』to her?

「Actually, when I mentioned onii-san to okaa-san, I've been told to bring you to the house.」

「No problem, I also wanted to ask her about various things too.」

「Iya~, it's a fast talk which saved me a lot of trouble.

Then, follow me.」

「Eh, now!?」

I've pretended to go to the bathroom to return home for a moment and explained the situation to Elena and Hilda.

It might be better for Elena and Hilda to have a mobile phone or smartphone too~.

***

Mai-san's house is located in a place a short distance away from Kochijoji Station.

There's a big house where history is felt.

「Onee-chan, welcome ho~me.

Eh? Visitors?」

What greeted us at the entrance―

was a little girl who looked just like Mai-san.

「N!? Mai-san's twin sister?

......

No, I'm not going to be tricked!!

You're Mai-san's okaa-san!」

「......hehehe......

How admirable of you to have seen through it!

Right! I'm Mai's okaa-san!!

As expected of the man who beat Mai!」

What farce is this......

Her actual age is probably around 40 years old but―

both her appearance and behavior are on the same level as a 10-year-old child......

「Stop it, okaa-san. It's embarrassing.」

「Oh, isn't it fine. It's a normal thing, isn't it?」

You always do such a thing, huh.

But, they look exactly alike.

I've heard that they've been mistaken for sisters but―

they've been mistaken for twin sisters, huh......

「Although I'm embarrassed to say, this is my okaa-san.」

Mai-san's okaa-san respectfully bows while pressing three fingers of each of her hands on the floor.[1]

「Well, since it's hard to talk while standing, please come in.」

Mai-san's okaa-san welcome us inside while having a dark smile.

「Have you had dinner yet? Please eat.」

Umu, it seems to be a very common Japanese dining table but......

the figure which is preparing dinner quickly looks like an elementary student trying to help.

「Really, I didn't expect that you were this young.」

「Ara ara, you're such a flatterer, ohohoho.」

No no, realize that it's not a compliment!

It already somewhat felt like playing house.

「Nonetheless, as I've heard from Mai, I can sense that you have a frightful 'ki'.」

「Ki?」

「Ah, even though I've said I can sense your ki, I, only Mai and I can tell so.」

Because Mai-san can sense magic, is that it?

「I also want to fight a person who seems to be so strong once.」

「Okaa-san!」

「I understand~

even without making such scary face,

I wouldn't do such a thing thoughtlessly for my age too ~.」

「By the way, does obaa-san not come?」

「That reminds me, you've said that you wanted to hear the story of our obaa-san.

I'm going to call her out now.」

「Good evening, I'm Mai-san's obaa-san.」

What appeared is an ordinary human.

She's refined and seems to be a little young to be called obaa-san.

However, when looking at these three people, no matter how you look at them, nothing but an obaa-san and twin grandchildren can be seen.

「Let's talk later, please help yourself.」

As we've been offered, we accepted and partook of the meal.

Every dishes that little girl okaa-san cooked were delicious, it seems to be what they called the『taste of mom's cooking』.

A mystery because despite her appearance, she seemed to be a person of suitable age when seeing this part of hers.

That reminds me, are Elena and Hilda having a meal properly?

When I checked the tracking beacon's video, Elena and Hilda ordered a pizza delivery and were eating with great relish while they were stretching the cheese with *nyoro~n*.

When we finished eating and drinking a cup of tea―

「While taking a rest, I'll tell you an old tale.」

obaa-san began to talk.

***

Going back exactly 40 years ago......

When the young obaa-san was on her way home and was walking down the street at night which had become a little dusky―

she heard a sound like a beast’s groan from a grove of mixed trees where she happened to passed by.

She was very scared but badly curious for some reason―

she peered into the grove of mixed trees cautiously.

Then―

an oni was there.

Although one might say it was an oni, it only had 1 horn and apart from that, it looked like a normal person.

And that oni was crouching down and growling in pain.

After she approached further―

somehow or another, this oni seemed to be injured.

Obaa-san returned home hastily and brought a first aid kit.

At that time, obaa-san seemed to be going to school to become a nurse and seemed to have a bit knowledge about nursing.

When obaa-san approached in order to treat the oni, the oni uttered words which obaa-san didn't understand and intimidated her.

But still, obaa-san somehow managed to convey with gestures that she was going to perform treatment and she treated the oni.

And when obaa-san finished the treatment and was about to go home―

the oni suddenly grabbed obaa-san's arm and she couldn't get away.

But obaa-san didn't understand its language, she guessed what it said was it wants her to stay with it and stood beside the oni for a little while......

And then, this and that happened......

like stamen and pistil *bleep bleep*......

It was morning when a sparrow was tweeting with *chirp chirp*, Obaa-san who had unknowingly slept woke up

However, the figure of the oni was gone―

what left in the place were―

a mantle which covered obaa-san as a futon when she was sleeping―

a paper which was made with some kind of skin―

and a pendant placed on that paper as a stone weight for it to not be blown away.

The pendant had a medal which had something like a family crest drawn on it.

And a paper on which characters of unknown language are written.

***

「My story is such.

Well, please pay it no heed, it's just an idle talk of an old person.」

So there are things the oni had left behind......

they are going to be clues.

「Can you show me that things it had left behind?」

「Yes, it's fine.」

Obaa-san brought out an old wooden box and showed me the three things inside.

「Excuse me, I'll look at them.」

First, the mantle.

┌─＜Appraisal＞────

│【Demon Lord's mantle】

│A mantle which can only be worn by the Demon Lord.

│Rarity: ★★★★

└─────────

Uwa!

Although I thought it might be possible but the『Demon Lord』!?

Next, the pendant.

┌─＜Appraisal＞────

│【Demon Lord's pendant】

│A pendant which has the crest of the Demon Lord drawn on it.

│Rarity: ★★★★

└─────────

With this, it's definitely clear.

Finally, the paper on which characters are written.

Or perhaps I should say, this is『Demon Language』!

┏━━━━━━━━━━

┃To the human girl whom I don't know the name either.

┃

┃ Thank you for treating my wounds.

┃ I must go home soon,

┃ I've left behind a pendant as thanks for the treatment.

┃ If you're in trouble,

┃ come to the demonkind's town with this.

┃ I'll come to help.

┃

┃ from Demon Lord

┗━━━━━━━━━━

It's somewhat a macho composition.

「You can read this letter!?」

Obaa-san is surprised.

「Actually, I've met someone who could be this person.

I'm going to meet that person again this time―

Is it fine for me to take a picture of these?」

「Yes, I don't mind.」

I took pictures of the cloak, pendant, and the letter.

「Since I want to show them to the other party, may I take a picture of obaa-san as well?」

「No, please forgive me.

I don't want for that person to see this old appearance of mine.

Take this instead......」

As obaa-san said so, she held out a picture.

It was a picture of obaa-san at the age of around 20 years old.

I took the picture from obaa-san―

and decided to meet the Demon Lord.

However, what kind of face would the Demon Lord make when I show him these.

I'm really looking forward to it!

[1] 三つ指 Mitsuyubi