After revealing himself, Aizen found Yoshio even more interesting than expected.
And…
More mysterious.
He not only chose a path that brought Aizen before him, he seemed to perceive all of Aizen's plans.
Upon arriving in Hueco Mundo, he immediately said he wanted to meet the king of this realm.
That was indeed within Aizen's expectations; once Ichimaru became Captain of the Third, it would be about time to subdue the great Hollows of Hueco Mundo.
Then he mentioned wanting Gin to become captain of the Third.
As if everything had already been seen through by Yoshio.
Yet Aizen didn't dislike that feeling.
He hated stagnation. He hated being predictable.
He didn't see variables in an otherwise perfect plan as bad; on the contrary…
They only excited him.
Still, Aizen considered his plan seamless and Kyōka Suigetsu's hypnosis perfect. How did Yoshio pierce it?
Aizen was clever and quickly thought of a possibility.
Seeing Aizen's favor toward him jump another ten, Yoshio knew Aizen had stepped into the "trap" he'd set.
He rubbed his forehead and activated the "The Animals" ability.
A crystalline shard precipitated from his hand.
When it appeared, Aizen looked over.
He gazed at the shard, pupils slightly dilating.
Yoshio then took out the single grain of sand he'd kept.
"To most people, these two things differ vastly in worth."
"But I'm different. I only care whether they interest me."
"Thank you, Captain Aizen, for bringing me to Hueco Mundo to obtain such a treasure of a grain. In exchange, I'll hand this to you."
He blew the glimmering mote that had formed at his fingertip toward Aizen; it drifted into Aizen's hand.
Aizen received it, the corner of his mouth curving.
"I see. No wonder you're immune to Kyōka Suigetsu."
"No wonder…"
"You know everything."
Before him, a structure like a black cavity opened again, and he stepped forward.
"Then I'll trouble you to remain in Hueco Mundo for a while. Once I've settled matters in Soul Society, come to the Fifth Division as my lieutenant, Yoshio-kun."
With that, Aizen's body vanished fully into the garganta. It sealed shut, and Aizen disappeared completely before Yoshio.
"..."
As Aizen vanished completely, Yoshio's ["Game Master"] mode finally faded, and he relaxed all at once.
The abrupt release after such pressure left his breathing ragged.
"Huff… huff…"
Yoshio flash-stepped repeatedly to get far from that area, then pressed a hand to his pounding heart.
"At last… talked my way through!"
That standoff with Aizen might have been only verbal, but it felt more exhausting than a big battle.
Still…
The result was good—he'd successfully bluffed Aizen.
If he guessed right, Aizen now…
Likely regarded him as some component of the Soul King?
The Soul King is the ruler of Soul Society and the creator god of the three realms. He carved the realms from primordial chaos, yet now only a main trunk remains, sealed in crystal in the Soul King's palace.
The rest was torn into fragments and scattered across the three worlds. Some retained rough forms—like the left and right hands, the heart—but most became small shards and residue.
For the creator of the three realms to end up like this—tragic indeed.
The Soul King's power is "omniscience and omnipotence." Of course, not literally in the theological or philosophical sense—but at minimum, it includes "seeing the future."
So from the start, Yoshio intentionally guided Aizen toward the impression that he could "see the future."
He stated Aizen's plans outright—easy enough to infer, since they appeared in the original story.
Aizen would seek out Baraggan and eventually recruit Hinamori and the others.
And Ichimaru Gin became Captain of the Third before Kuchiki Rukia graduated; yet right now the Third still had a captain with no sign of retiring.
Therefore, before Rukia graduates next year, something must happen to force the Third's captain to step down!
Yoshio thus surmised that Aizen's target this time was the Third's captain.
After creating the impression of "future sight," he activated the [The Animals] to split off a portion of his soul, handing the soul fragment to Aizen.
The [The Animals] derives from Matsumoto Rangiku's soul ability, whose essence comes from a fragment of the Soul King in her soul.
While Yoshio's created pill wasn't a Soul King fragment, it was similar in effect.
The prior dialogue plus Yoshio's soul shard should be enough to make Aizen regard him as someone connected to the Soul King—possibly a fragment of some part.
Hence Aizen left: with that belief, Yoshio naturally became different from other Shinigami.
The Soul King's enemy is the Shinigami; even if Yoshio isn't truly the Soul King, knowing the world's essence so clearly, he certainly wouldn't stand with the Shinigami.
But for now, Aizen still needed to execute his plan, so he left Yoshio in Hueco Mundo for the time being.
Which…
Wasn't so bad.
Yoshio didn't want to be entangled in Aizen's plan anyway—he just hoped Aizen would, for his sake, refrain from slaughtering everyone.
Such is the lot of the weak: when you lack strength, even your life and death are in others' hands.
Yoshio looked ahead. After recovering, he stopped roaming—Hueco Mundo was too dangerous.
He had exited ["Game Master"] mode; his strength wasn't what it had been.
He had permanently acquired Tanimoto Toru's [Special Beam Cannon], and one-time uses of [Fireball] and [Black Sun], but running into a Gillian or stronger here would still be perilous.
If possible, though, there was someone he wanted to find.
In Hueco Mundo, there was indeed someone easy to befriend—
Coyote Starrk!
The future Espada No. 1, a self-evolved Vasto Lorde.
If he could find him, he might quickly earn his friendship.
Assuming he wasn't crushed by Starrk's spiritual pressure first.