"Sister's ex-boyfriend?"
Shinobu's perfectly maintained gentle smile shattered the instant she heard Shuya's claim. She instinctively gave him a long, hard stare.
Black hair, black eyes, ridiculously good-looking.
At first glance he seemed ordinary, but the more you looked, the more he gave off this unfathomable vibe.
So this was the type her sister liked?
"I get it now!" Tanjiro exclaimed, eyes wide with sudden realization. "No wonder these two Demon Slayers didn't recognize you, Shuya-san, but you knew them! So your ex-girlfriend was actually a member of the Demon Slayer Corps? That explains everything."
"Hey, Miss Kocho," Shuya said with a smile, not denying a word. He extended his hand toward her. "For your sister Kanae's sake… can we make peace?"
"Heh."
Shinobu let out a cold laugh.
She quickly came back to her senses. She had lived with her sister their entire lives, depending on each other for everything. If Kanae had actually had a boyfriend, there was no way Shinobu wouldn't have known. Something that important? Her sister would never have kept it secret.
This guy was obviously lying.
Shinobu slapped his hand away. "You really think I'd believe that?"
"Why not?" Shuya asked softly.
"If it's true, then answer me this: Why have I never seen you before?"
"And where were you the day my sister was killed by a demon?"
At first Shuya had only said it as a casual tease. But seeing how seriously she was taking it, he suddenly felt like leaning all the way in.
He thought for a second, then started spinning his story—90% lie, 10% truth.
"My name is Shuya. From my name alone, you can probably guess I'm not from this country. I'm from the large nation to the west of your islands.
"About two and a half years ago, I came here to study abroad and met a girl who was as beautiful as a flower in full bloom.
"That girl was your older sister—Kanae Kocho.
"Even though we only spent one day together, her image was burned into my heart forever.
"That day we talked about so many things—the stories of demons, the Demon Slayer Corps, and her two little sisters.
"One was a reckless, hot-tempered girl—little Shinobu.
"The other was a withdrawn girl who didn't know how to talk to people—Kanao.
"I told her I wanted to take her and her sisters away from this country so we could live normal lives.
"But Kanae refused. She said she had made a promise with her sister. She didn't want the pain she had suffered to happen to more people, so she would stay and kill as many demons as possible.
"Not long after that, I returned to my home country.
"It was only recently, when I came back to this country, that I heard the news that Kanae had already passed away.
"As for why she never mentioned me to you… I have no idea."
"This…"
After listening to the whole story, Shinobu started to doubt herself.
Her sister had been killed by an Upper Rank demon two years ago.
Her own personality had only started copying her sister's gentle smile after that day.
If he wasn't someone who knew her past, there was no way he could know she used to be impulsive and short-tempered.
The promise between her and her sister was their private secret. She had never told anyone.
And right before she died, Kanae had said almost the exact same thing—urging her to leave the Corps and live a normal girl's life.
Could it be…?
Was this man really her brother-in-law?
"Although the description is a little different from what Kanae told me, you must be the 'little Shinobu' she mentioned, right?" Shuya said gently. "If it's possible, could you take me to the Butterfly Mansion someday?
"I'd like to see the place where Kanae once lived."
Of course Shuya had his reasons for saying this.
In the Demon Slayer world, souls were real—just rarely seen.
Besides the occasional appearances of dead characters in life-flashing visions or to guide the living, most souls only showed up to the people closest to them at the very end.
If Breathing Techniques were essentially an alternative way to use life energy (Nen), then these lingering souls might be similar to the "post-mortem Nen" concept from Hunter x Hunter.
With the power of his contracts, there might actually be a chance to revive someone using that concept.
Unfortunately, even after checking with Gyo, he hadn't seen any sign of Kanae's spirit near Shinobu.
Based on everything he knew, he guessed that in this world, souls of people who died with strong regrets might stay attached to the place that held their strongest memories.
For Kanae, that would be the Butterfly Mansion where she lived with her sister Shinobu.
Since he had no plans to join the Demon Slayer Corps directly, using the late Flower Hashira as an entry point seemed like a good way to get there.
After all, dead people can't talk back… right?
By the time they could speak, he would have already achieved his goal.
Naturally there were other ways to reach the same result.
But honestly, he was mostly doing this because he found it hilarious to mess with the cunning, black-bellied Shinobu.
He was really looking forward to the face she would make once the lie got exposed.
"…"
Shinobu fell silent.
She glanced at Shuya's somewhat sorrowful expression and started to believe the identity he had made up.
"Sister Kanae and Shuya-san are so pitiful… They loved each other but couldn't be together."
After hearing the story, Nezuko's eyes filled with tears as she hugged Shuya's arm tightly.
Shuya smiled and gently patted her head, then looked at Shinobu.
"If it's okay with you, let me take care of you from now on… little Shinobu?"
The moment she heard "little Shinobu," Shinobu snapped back to reality.
She looked at Nezuko clinging to Shuya's arm with teary eyes, then at the tall, beautiful, and ridiculously strong Saeko standing quietly beside him, and finally at the gentle-looking Shuya.
She came to one firm conclusion.
This man is definitely a scumbag!
There is no way she would ever acknowledge him as her brother-in-law!!