Someone's mutterings are exactly in line with Chihiro's understanding.
Dual personalities, or multiple personalities.
Or so called dissociative identity disorder (DID), or something like that.
（Yes, that's right, "Nii-san"）
A voice rang out in his head.
It was similar to Hazuki Marika's [Telepathy], but the source was not external, but internal.
In other words, it was the voice of "someone" inside Chihiro.
And again, the mouth moves by itself.
「I am Chisato. I am the personality created by Hana-san's thoughts and my brother's ability. ...maybe?」
「Wait, is that Chisato-chan who speak... not Chihiro-kun?」
Aika blushed at the unfamiliar way of addressing her. But surprisingly, she does not seem to mind being called "Ane-sama" at all.
Seeing such an exchange between them, the other members of the group react in their own ways.
Maria smiles from her blank expression. Riko blinks her eyes with a look of dismay.
「Nii-san...? Do you mean Chihiro?」
「Yes, that's right. But I'm a part of him, I guess. Though I'm not sure about that, since I've only recently become conscious properly. And somehow, I call him my brother」
Since she seems to be another personality based on Chihiro, it certainly feels right to think of her as a "little sister".
More specifically, she is his "twin sister".
Although Chihiro, being the youngest, has no idea what younger siblings are like.
（Nii-san, would you have preferred me to be Hana-san's daughter?）
A voice saying in his mind.
It is a strange feeling, to hear a voice that sounds so much like his own, coming from somewhere else.
「No, I think I'd like to have my first child with Aika...」
「What are you talking about all of a sudden? You disgusting」
Chihiro answered out loud, and Hana gave him a terrible glare.
（Nii-san.... It's okay if you just talk in your mind）
（Haha... I'll be careful）
This time, the conversation succeeded in silence.
It seems that Chisato can trace Chihiro's thoughts to some extent. Chisato also seems to be able to convey her intentions to Chihiro without any explanation.
（Chisato, can you use my body too?）
（Only while Nii-san gives me permission. So, if you don't think it's a good idea, I can only watch）
Although it was a strange feeling to have another person inside of him, there was also something that felt right.
At least it's not too uncomfortable.
（A little sister, huh?）
（Yes, because we are the same person, maybe...）
It might be easier to understand if he think of her as an upper version of the self-question.
But then Hana's voice came.
「Wait, so, you really have dual personalities? Not just Izumi-kun's acting or something」
Naturally, she cannot hear the conversation in his mind. So, she does not know that Chihiro is beginning to be convinced.
「Hana-chan, this is exactly where you start to doubt me」
「That's true. If I admit it, it means I wanted this situation」
――Misumi Chisato, a fictional character, whom Hana dreams exists.
There is nothing wrong with that.
If it is only that, there is no problem as long as it is kept inside of Hana, but if her strong desire has become an ability and realized, it is indeed embarrassing.
Whether she is happy or not is probably secondary.
（I might understand her feeling a little...）
（Yes, you're right.... I'm also embarrassed to have people guessing the origin of my "Mind Reading"）
While sympathizing Hana and to prove Chisato's existence, Chihiro tries to surrender control of his body to Chisato.
Chisato smiled and nodded his head when Chihiro entrusted his body to Chisato.
「...Even if you say so, it's hard to prove, huh? Oh, that's right」
While Chisato was saying that, she thought of something.
She shifted her gaze from Hana to Riko and smiled.
「Yes. Riko-san, can I borrow your [Illusion] for a moment?」
Immediately after those words.
The girls looked at the back of Chihiro's head and each let out a short voice.
Chihiro, who was curious, turn around to see what's going on.
And he saw himself.
No, it was not.
Not exactly Chihiro himself.
The base is definitely Chihiro, but the details are different. The person in the school uniform has semi-long hair and slightly lighter skin color. Her arms and legs are slightly thinner than Chihiro's, and her breasts have a modest but female-like fullness.
Chisato smiled at him.
Her smile gives a soft impression that softly envelops the viewer.
Also, her voice is not borrowed from Chihiro's vocal cords, but is definitely her own voice.
Unable to believe what they were seeing now, Chihiro extended his hand to Chisato.
So did Chisato. She does the same and tried to put her palm to Chihiro.
However, Chihiro's hand did not feel anything.
Chihiro's hand slipped through Chisato's palm.
It is an illusion.
「It is Riko-san's ability」
Chisato has no body of her own.
Therefore, other people can only see and hear with Chihiro's eyes and ears, and speak with his mouth.
But now they can see and hear her after she borrowed Riko's ability to help her.
「Huh? So, Riko... do you mean to say that you could make a sound as well?」
「Oh, yes. I've been able to make it for a while now. Didn't I tell you?」
"No, I haven't heard that at all," Chihiro thought.
Well, it can't be helped that she doesn't have many chances to use her [Illusion] in her daily life.
However, is Chisato could easily borrowed Riko's abillity?
Chihiro glanced at Suzu. Sure enough, she is looking at Chisato excitedly.
「You can do that?」
「Yes. However, even if I borrow it, I can't use it freely. It is not the same as copying or looting」
Shortly, all Chisato can do is project herself as an illusion.
She can change her clothes and hairstyle, but she cannot change her body shape drastically or pretend to be someone else. In this respect, she is bound to the image of "Misumi Chisato" constructed by Chihiro and Hana.
Moreover, she cannot be far from Chihiro――perhaps more than ten meters away.
It also seems that Chisato is partially borrowing Riko's ability which is connected with Chihiro's ability of [Domination]. Nevertheless, Chisato herself seems to have only vaguely thought that she could do it, and the details of the principle are unknown.
「I think Hana-san will trust me, too, don't you?」
The two brother and sister――or should they be called――turned around together.
And to Chisato's word, Hana was in tears.
「I was moved」
Apparently, Hana is crying tears of joy.
Riko looked at her and muttered in confusion.
「Umm, Mishuku-san, aren't your characters different?」