"Posthumous Nen," as the name suggests—Nen that can only be activated after death.
For example, the ability "Million Reincarnation Cat" of Camilla, the second princess of the Kakin Empire, can trigger passively after her death, taking the life of the murderer and resurrecting her.
Similarly, after Catwoman Nephelpito was killed by the corrupted Uncle Gon, to prevent Gon from further pursuing trouble with the Ant King, she activated Posthumous Nen, using "Toy Repairer" to continue manipulating her headless corpse to attack Gon, stopping only when completely destroyed.
There's also the Posthumous Nen collected by Kuroro—"Paired Destroyers"....
Sisko's proactive resurrection...
In conclusion, "Posthumous Nen" is flexible in use; it can be used for self-rescue or to exact revenge and impact others, characterized by—
"intensity," "obsession," "desire power," and other features.
But the person before them is clearly not... one, Minamino Guangzhi is just a regular traveling merchant, not a Nen user...
Two, this is the Demon Slayer World within Roy's sea of cognition, as a local "indigenous person," without Roy's guidance, he couldn't have contact with Nen, doing something beyond his cognitive world, so then...
There's only one possibility—
He is a residual soul!
Spirit: specifically refers to the human supernatural and non-material components.
It is the concrete manifestation of human spiritual will transcending the body.
This can be seen when Tanjiro tries to help Minamino Guangzhi up, only for his hands to pass through his body.
'Ghost... he is another kind of ghost...'
With powerful entity ghosts like Sato Takeshi, Doihara in front, Tanjiro stared blankly at his hands passing through Minamino Guangzhi, momentarily unsure what to call him.
Minamino Guangzhi himself, however, remains optimistic, or perhaps as a traveling merchant who has traveled far and wide over the years, he has long developed the skill of speaking human words to humans, ghost words to ghosts, and cheerfully said to Tanjiro: "Benefactor, please do not worry. Having been killed by an evil ghost, I am fortunate enough to see the world one last time, already a blessing."
Indeed, as Minamino Guangzhi said, his residual soul is not stable, visibly thinning in the cold wind.
"Nii-san, he's going to disappear!" Tanjiro exclaimed in panic....
Tonight he had seen too many remains, unable to bear seeing another "life" wither away.
However, is Minamino Guangzhi really still a living being?
Roy contemplated...
In silence,
coating his right hand with Nen, he tried following Tanjiro in helping Minamino Guangzhi.
To the surprise of Tanjiro and Minamino Guangzhi... he was able to lift the residual soul of Minamino Guangzhi.
As if Minamino Guangzhi had an "entity" at this moment, enough to baffle anyone.
Minamino Guangzhi, astonished, looked at Roy, bowed and saluted again: "Thank you, benefactor, for rescuing me. I feel much better now."
Indeed...
"Nii-san, he's really become much more solid...."
Tanjiro curiously circled around Minamino Guangzhi.
Roy remained silent, able to intuitively feel his own "Nen" being consumed.
In other words, Minamino Guangzhi can exist and temporarily maintain his current state, based on continuously supplying Nen.
Once he withdraws the "supply," Minamino Guangzhi's fate is dissolution.
Essentially... Nen ability itself relies on the Six Aura Types, integrating "jing," "qi," and "shen" into one...
It's a reflection of "emotions," "will," "personality," and all other measures of this biological "human" as a "virtual quantity"...
In summary—it's the "My Power of Thought" relying on "numerical values" and "mechanism"!
'Because of Nen, can I touch the soul?'
Roy had an epiphany... at this moment, the panel suddenly flashed twice and popped out....
A new section opened up under "Nen Ability Form Change"—
"Nen Ability Property Change"!
Roy was stunned... what is this? A reward for exterminating evil ghosts?
He only remembered the booklet given by his great-grandfather mentioned "Property Change" briefly, but did not introduce specific training methods.
Or perhaps... the other party felt he had just opened his acupoints, and had not systematically developed the Nen ability, going too deep into "Property Change" sustaining was too early, thus only giving him half of the content.
But.....
Maha would not have thought that Roy's Nen ability is "Gate of Cognition"...
Ever since first entering the dream, it has been continuously exploring and developing his Nen ability....
Then, the question arises...
'After returning, should I ask him for the remaining half regarding "Nen Ability Property Change" content?'
Roy pondered for a few seconds, ultimately deciding... there's no rush.
Food must be eaten bite by bite, the road must be walked step by step, for now it's important to improve one's "numerical value," learn how to "Full Concentration" with "Sun Breathing."
Many thoughts flashed through his mind instantly...
Roy came back to his senses, bluntly telling Minamino Guangzhi: "No need to rush to thank me. Ultimately, you will still disappear."
Minamino Guangzhi is not a Nen user, his body has been destroyed, there's no possibility of reviving using "Posthumous Nen."
The barely remaining "residual soul" is also sustained by Roy's Nen... and Roy can't possibly always support an unrelated person.
"I already said being able to see this world again is already a blessing." Minamino Guangzhi smiled and said,
"But once dispersed, it really is gone..." Tanjiro saw his indifferent expression, couldn't help but worry for him.
Roy glared at him: "Shut up!"
Calmly looking at Minamino Guangzhi, honestly admiring this traveling merchant for still having such a serene attitude in this situation: "Your excellency is indeed optimistic...."
"If you still have unfinished business, feel free to speak, the two of us brothers have the ability, will try to fulfill..."
"Nii-san is right, I can help too." Tanjiro blurted out, then quickly covered his mouth, daring only to peek glancingly at Roy.
Luckily, this time Roy didn't hold it against him.
"There is one thing." Minamino Guangzhi gazed toward Sagiri yama, draped in a white veil of snow, his knees softened, once again kneeling at Roy's feet...
"I implore the benevolent one to take me to see my daughter one last time, with this... I would be satisfied."
"How old is your daughter?"
"One and a half."
"Can she call you Papa?"
"She can." Minamino Guangzhi said happily: "She not only calls me Papa, but also learned how to walk."
"You don't know, every time I come back, she wants to lay on my belly, shouting "Papa," "Papa," while drooling all over my face...."
"I even thought of waiting for her to grow a bit more, to braid her pretty little pigtails, take her to Tokyo for a trip, try the famous sticky rice dumplings...."
"And by chance visit the Mutou Family's children's clothing store, buy her some nice little dresses, watch her in front of the mirror feeling pretty...."
Minamino Guangzhi rambled on....
He seemed to have endless things to say...
Roy didn't interrupt him, just listened silently, while beside him, Tanjiro's tears flowed unrestrainedly.
The dying words of Doihara, "This damned world!"
suddenly surfaced in Tanjiro's mind.
The young man couldn't help but touch the axe tied at his waist.
The axe blade reflected the moonlight, flashing with a biting cold light...