One afternoon, Alice summoned me to her general store. I wasn't sure why, but I had a nagging feeling that something was different from our usual interactions.
Normally, Alice stayed hidden right next to me, invisible to the world. If she had a quick errand or a minor point to discuss, she would have just spoken up then and there. The fact that she had gone out of her way to specify a location and ask me to visit suggested a matter of some importance.
As I approached the familiar shop, my suspicions were confirmed by another oddity. The sign hanging on the door was set to "Closed."
The shop almost never saw a single customer, yet the sign was usually kept on "Open." Seeing it flipped made me certain that this was going to be a serious conversation.
When I stepped inside, Alice was already sitting at the back counter. It wasn't the shopkeeping split body she usually used—the one that wore a kigurumi. Had she zipped behind the desk the moment I opened the door? I decided to stop wondering. Such thoughts would only ruin the gravity of the moment.
"Welcome, Kaito-san. I'm sorry for calling you here so abruptly."
"It’s fine, but..."
"You want to know what this is about, right?"
"Yeah."
Surprisingly, Alice moved straight to the point without her usual antics. What on earth was she planning to discuss?
"Well, Kaito-san, I have a proposal. Would you like to try learning how to use a 'Heart Tool'?"
"...Huh? You mean like your Hecatoncheir, or Iris-san’s Apocalypse?"
"Exactly. A Heart Tool... magic that forges a weapon from a powerful heart."
"...Wait, is that even something I can learn?"
I didn't know what she was aiming for, but the subject itself piqued my interest. According to Alice’s previous explanations, a Heart Tool was a spell that turned one’s very soul into a weapon. While the properties varied wildly between individuals, it was an incredibly potent form of magic—and Alice’s own ultimate trump card.
As a man, I couldn't help but feel a certain thrill at the idea of a personal weapon. But could I really learn it? My talent for magic was undeniably poor.
"It’ll be fine. Remember when I explained them to you before? In my original world, ninety percent of humans could use Heart Tools. Setting aside the difficulty of mastering them, simply manifesting one is easy."
"I see..."
"What's more, housing the seed of a Heart Tool in your soul is incredibly simple. All it requires is for a human to touch the Heart Tool of someone who satisfies one specific condition. That's all. Now, once it's housed, the time it takes to actually awaken varies from person to person."
"And what’s the condition?"
It sounded like a powerful spell, yet the requirements for learning it were surprisingly basic. Then again, the "condition" might be the real hurdle. Still, the fact that Alice was bringing this up meant she must satisfy it.
"It’s actually quite straightforward. The wielder must cherish the person from the bottom of their heart. In my world, children would touch their parents' Heart Tools shortly after birth. That’s why almost everyone could use them."
"I see."
"However, in this world, the only person who can learn a Heart Tool... is likely you, Kaito-san."
"...What?"
"The reason is simple. Iris is currently just a part of my Heart Tool, so I’m the only one in this world who can use one. And you are the only human I cherish from the bottom of my heart."
Alice spoke with a slight flush on her cheeks, perhaps feeling a bit embarrassed by her own confession.
"As an aside, though I don't fully understand why, I believe Heart Tools can only be housed within humans. I haven't been able to verify this thoroughly since there aren't many people I care for, but the seed wouldn't take root when I tried it with Fate-san or Kuro-san."
"I see. So that's why you called me..."
"Yes. Well, there's a chance it won't work since our worlds are different, but it's not a difficult process. Why don't you try touching my Hecatoncheir?"
"Alright."
To be honest, I still had questions. Why was Alice trying to teach me this so suddenly?
If I had to guess, perhaps she was anticipating a situation where she wouldn't be able to protect me. She might be trying to give me some means of self-defense.
If that were the case, Shiro-san’s upcoming trial was the most likely reason. I didn't know the details of the trial yet, but there was no harm in being prepared. Besides, I was genuinely curious about the Heart Tool.
With those thoughts in mind, I reached out and touched one of the glowing meteors of Alice’s Hecatoncheir. For a fleeting moment, I felt a deep, heavy pulse resonate within my body.
"...Well? How do you feel, Kaito-san?"
"Just now... it felt like something pulsed deep inside me. But I don't feel anything anymore."
"It seems the seed took root without any problems."
"Wait, is that it? It’s already inside me?"
"Yes. It's housed within you, though I can't say when it will awaken. Some people awaken immediately, while others take years. A few people never awaken at all and live their whole lives with the seed just sitting there."
"Understood."
"One day, the name and ability of that Heart Tool will simply pop into your head. That will be your awakening."
It was a shame I wouldn't know the nature of the power immediately, and I had no idea if it would awaken in time for Shiro-san’s trial. Still, I found myself looking forward to it.
"Now then, that's enough of 'Serious Mode.' Let's have some tea!"
"That was a sudden shift..."
"Come on, I'll brew the tea. You provide the snacks, Kaito-san!"
"You're just naturally making me provide the food now, aren't you? Fine, I have some."
"All-you-can-eat! Thank you ve—gyah!?"
I let out a sigh as I watched Alice return to her usual playful antics without ever explaining her true reasons. I trusted her, though. If she wasn't saying anything, she must have a purpose for it, so I decided not to press the issue.
With a second sigh, I reached into my magic box and pulled out a generous portion of sweets to pair with the tea.
Dear Mother, Father—Without quite understanding how, a power called a Heart Tool has come to reside within my soul. It’s unclear when it will awaken, but I hope it’s soon. I really want to know what kind of power it is.
While preparing the tea for Kaito, Alice spoke to Iris in the silence of her mind.
(As expected of Kaito-san... the compatibility with my Hecatoncheir is incredible.)
(Even if it requires certain conditions to manifest, it is a formidable Heart Tool. A rare type, as well. And you're right—the synergy with your own power is staggering.)
Kaito’s Heart Tool had not yet awakened. However, it definitely existed within him. Because of that, Alice’s Hecatoncheir could borrow the strength of the one with whom she shared a bond. She could borrow the power of his Heart Tool.
Consequently, Alice already knew both the name and the ability of the power sleeping within Kaito’s soul.
(My primary goal was different, but this is a happy surprise. Depending on how the battle goes, this could be the trump card that changes everything. Plus, the fact that its effect perfectly reflects our status as the 'Best Couple' makes me super happy. I really want to brag about it.)
(Save the flirting for later.)
(Yes, yes. Well then, while I have tea with Kaito-san, I'll start refining my schemes to include this new factor.)
(I told you to call it a strategy meeting...)
Rejoicing over the unexpected trump card they had obtained, Alice and Iris began meticulously adjusting their combat plans for the upcoming decisive battle.
??? "Wow, Kaito-san and Alice-chan really are the best couple! Their hearts are perfectly in sync!!"
Serious-senpai "...So, what kind of Heart Tool is it?"
??? "Oh, that’s a secret for now. But you might be able to guess. Here's a hint: it’s a Heart Tool that is perfectly 'Kaito-san,' and its compatibility with Alice-chan’s Hecatoncheir is beyond perfect! It’s so important, I’ll say it again—beyond perfect!"
Serious-senpai "...Your high energy is really annoying."