"One piece…" the Goblin repeated once again, looking toward its invoker with an eye full of greed.
Jin swayed slightly, still shaken by the succession of unexpected events. However, the Goblin's appearance was striking enough to draw his attention.
Not only that, but the bustling market around them could only stir greed in the hearts of those present.
Jin could see gold, magnificent women in near-nude attire, objects from places he would once have called fictional.
"Is this m-my innate technique?!" he thought while observing his surroundings.
Surprisingly, Jin's innate technique came with a Domain Expansion.
A rare phenomenon, but not impossible.
Hakari and Higuruma are people similar to him, according to his understanding of this kind of anomaly.
Beyond this rare aspect, all Domain Expansions of this type showed no immediate lethal capability.
A logical situation, because Domain Expansions were not as lethal in ancient times.
According to the wise Tengen, Domain Expansions were once merely supports based on fixed rules, a bit like Field Spells in Yu-Gi-Oh!.
The difference is that sorcerers don't mess around: every Domain Expansion can be deadly.
"Hm… I see, you want something," Jin asked while observing the Goblin behind the stall of expensive-looking objects.
The entity simply sketched an even more unsettling smile before slowly nodding toward Jin to confirm his words.
[Domain Expansion: The Causal Market]
Jin hadn't fully grasped this place, but he understood the essentials after digesting the basic information of his innate technique.
This Domain Expansion essentially relies on the law of the market, which Jin recalls from his economics studies.
Supply and demand.
Jin has the right to ask the Goblins for anything, but the price would be proportional to the value of the object "for Jin."
For example, if Jin asks the Goblins to eliminate Sukuna without possessing something of greater value than the latter,
the Goblin will refuse the deal.
He would need to rephrase his request to obtain something leading to the desired results, but also within his budget range.
This situation is called: substitution in economics.
When a customer seeks an alternative to the desired product because the cost is deemed too high.
Beyond substitution,
the Goblin can also propose other "commercial agreements" to Jin that it deems fair.
All of this seems incredible, doesn't it?
Unfortunately, there is a downside to this seemingly miraculous power.
It is possible for a person within the Domain to also bid on Jin's offers and compete with him for a power or object.
Thus, Jin is a customer of the Goblin.
'On the other hand, I have an ace up my sleeve,' he thought while recalling an important aspect that the Goblin allows him to use, unlike his opponent.
Credit.
Jin can obtain credit from the Goblin during bargaining with the Goblin.
Credit is an aspect tied to VIP status, which Jin's opponent does not have access to in the Domain.
In theory, he can have anything and pay later.
In case of non-payment within the time set by the Goblin, Jin will be considered insolvent by the Goblin.
What does that entail?
In three words: confiscation and penalty.
"I want to heal this woman," Jin declared in a serious tone.
The Goblin nodded toward him while maintaining its playful attitude, then offered him a paper with inscriptions.
Jin didn't hesitate to take the paper extended by the Goblin after noting his shikigami's cooperation.
"Indeed, worthy of a power based on capitalism," he thought inwardly while observing the cost of his request.
"Problem, Dad?" Nayuta asked in an unusually hesitant voice.
The disinterested and confident little girl no longer existed at that moment.
Jin perceived only a worried kid after witnessing a scene she shouldn't have seen from her father figure.
"Sorry, sweetie, Dad's going to fix everything," he said on impulse, without thinking too much.
For him, those words were the most natural to say to Nayuta.
"Okay," she replied while clenching her two small fists before nodding toward him.
Jin relaxed thanks to this small interaction. He now had clear enough ideas to step back and reject the Goblin's deal.
It was just a pure scam.
[Transaction number — 001]
[Object of the agreement: healing service.]
[Description: Client Jin Itadori consents to cede a measurable and sufficient portion of his vitality to fully restore the current injury of the one named Kenjaku.
The amount deducted will be determined according to the principle of causal equivalence between the two present subjects.]
[Warning: No further negotiation will be accepted after validation of the agreement.]
[Contract drafted and approved by the administrator of the causal market.]
[Please sign here.]
"What?! You're unhappy with the deal?" the shikigami declared in a doubtful tone.
Jin nodded but didn't take his time to explain further.
Kaori's body could perish in the meantime.
"I would like you to transfer to me Kenjaku's experience in using Reverse Cursed Technique, but I intend to pay with soul information," he replied in a calm voice.
"You don't want to lose any of your vitality, but also want more? Haha," the Goblin burst out laughing.
The entity's laughter echoed loudly through the causal market but eventually stopped. Something welcomed by the duo's ears.
It stared at Jin for a moment before handing him another contract.
[Transaction number — 001]
[Object of the agreement: Kenjaku's Reverse Cursed Technique]
[Description: Client Jin Itadori consents to cede soul information that he judges sufficiently precious to suffice in obtaining Kenjaku's knowledge and experience here present in the use of Reverse Cursed Technique.]
[Warning: The level of Reverse Cursed Technique may be degraded if the spiritual knowledge provided is not judged sufficiently precious.]
[Another warning: No further negotiation will be accepted after validation of the agreement.]
[Contract drafted and approved by the administrator of the causal market.]
[Please sign here.]
Unlike the first time, Jin signed the agreement with the Goblin without a moment's hesitation.
"So? What information are you going to lose?" it said while narrowing its eyes at Jin.
"Here, I think this is sufficiently precious," Jin declared while tossing a sphere toward the Goblin.
The entity froze for a moment upon receiving the sphere before bursting into laughter again.
"You really are a cunning man," the Goblin muttered while storing the sphere of Toji Fushiguro's soul information.
Jin had managed to obtain a bit of DNA thanks to Gong. Even though the broker had looked unfavorably on his request for Toji's hair, he agreed to get some after Jin provided enough money.
That's also why Jin is clearly in the red at the bank even though he had received a lot of money from the parental bonus tied to Yuji's birth.
'I could always try to get my own Toji later, or I'll just make a deal with Naobito and Ogi,' he thought inwardly while receiving the knowledge related to Reverse Cursed Technique.
"A piece of advice, my dear client. You'd better heal her quickly~," the shikigami suggested.
Jin didn't immediately understand its words but realized their true nature upon checking his cursed energy.
"I…" Jin couldn't finish his words because he lost strength in his legs.
He was exhausted.
In a short time, he had fought a battle requiring a lot of concentration and subtle use of his cursed energy.
He had even been pierced!
Beyond the small fight with Kenjaku, he had recklessly used his Domain Expansion for the first time.
His body couldn't keep up.
"No need to come, I'm fine," Kenjaku declared while casually rising from the ground.
As Jin's Domain Expansion slowly shattered,
Nayuta and Jin had the impression of witnessing a surreal scene before them.
Kenjaku casually dusted herself off, even though she bore an empty hole where her heart should be.
The question everyone asked while witnessing this morbid scene was: how did she survive?
As if reading their minds, the blood began to float in the air to form a sphere at the tip of her finger.
Kenjaku had herself ensured the circulation of her blood thanks to Kamo's blood manipulation technique.
That's why Jin noticed nothing suspicious. Kenjaku had not deployed Reverse Cursed Technique, and the cursed energy was concealed by that of the barrier.
"You really thought crushing my heart would be enough to take me down? Too cute~," she said while leaning over to carry Jin.
"N-no," Jin tried to protest, but Kenjaku royally ignored him before carrying him like a princess.
For the first time since his reincarnation, Jin felt shame.
Unfortunately, he hadn't noticed the silhouette watching the scene a few steps back.
"Kenjaku is cool," Nayuta muttered, her eyes shining with admiration.
⸻
Author's note: At the level of Gojo, Sukuna, Kenjaku, and Yuta, something like losing their heart is nothing.
Unfortunately, Jin was too blinded by the scene of Kaori's body losing strength due to a fatal blow. Anyway, nothing guarantees that Kenjaku wouldn't have committed suicide.
The character is extremely disturbed.
I'm going to explain the basis of Jin's innate technique here because I'm aware I didn't really develop it due to the lack of a real opponent in the Domain Expansion.
To put it simply, the Goblin is a supervisor or intermediary of the causal market. It evaluates the quality of Jin's and his opponent's transaction proposals during negotiations. (As a VIP, Jin can get credit here to outbid.)
Jin can request anything and the causal market will produce it (a bit like Mai and Yorozu's power), but there is an important element:
Jin must be able to pay! Same for his opponent if they want to buy something from the Goblin. Otherwise, they will suffer penalties and confiscation of the requested object.
Beyond purchases, the causal market performs other operations that Jin has access to as a VIP. (The intruder can also access them at a price, because the law of the market is impartial, like Higuruma's power.)
So that's the essentials, but you'll encounter economic concepts here, like rebound effect and others.