The Letter  

"However, Captain Gin was still quite weak at the time. Even if he discovered Captain Ailin's secret, with Ailin's immense strength, he would have easily eliminated Gin without a trace if he found out.

Fortunately, I had gained some recognition within the Seireitei, and Gin approached me for help in transferring to another division.

Later, Gin came into contact with Captain Hirako of the Fifth Division. Shortly after, Captain Hirako and three other captains met with misfortune...

After decades of training, Captain Gin felt his strength had improved somewhat. He contacted me secretly and revealed everything he had told Captain Hirako about Captain Ailin.

I will now record all the information I have gathered about Captain Ailin.

Captain Ailin entered the Shin'ō Academy from the Rukongai 146 years ago. His performance during his time at the academy was exemplary..."

Ailin raised an eyebrow in surprise. He hadn't expected Aizen's investigation to reach so far back, tracing his history all the way to his academy days.

However, the claim of his exemplary performance elicited a scoff from Ailin.

It seemed that either some teachers at the Shin'ō Academy had altered his records, or they had exaggerated his performance out of fear of offending him when Aizen conducted his investigation.

After all, during his time at the Shin'ō Academy, Ailin, despite his lofty ambitions, lacked the natural talent to match.

To call him the worst student would be an exaggeration, but even describing his performance as "mediocre" would be generous.

Fortunately, even then, Ailin understood that regardless of one's overall strength, speed was always an asset.

So, even though his skills in Zanjutsu (Swordsmanship), Hakuda (Hand-to-Hand Combat), and Kidō (Demon Arts) were lacking, his Shunpo (Flash Step) was among the best in his class.

Ultimately, during his sixth year, Ailin's exceptional Shunpo skills earned him a special recruitment into the Second Division.

Ailin continued reading, curious to see how Aizen would spin his narrative.

"After graduating from the Shin'ō Academy, Captain Ailin joined the Second Division. During his time there, he gained recognition from his fellow squad members for his proficiency in Kaidō (Healing Arts)."

The letter accurately documented his experiences from his academy days to the present, including all the major events he had been involved in.

Ailin had no complaints about the accuracy of the investigation thus far.

However, the next part delved into Aizen's "suspicions" about him.

"After hearing Captain Gin's account, I investigated Captain Ailin's history and discovered his motive for conducting 'Hollowfication' experiments.

It is well known that Captain Ailin and Lady Haruko are deeply in love. However, two years after their marriage, they spent a significant amount of time apart. Based on my investigation, I learned the truth from Captain Unohana of the Fourth Division.

Although Captain Ailin had only been the Captain of the Sixth Division for less than two years, his reiatsu had already reached an exceptional level, far exceeding that of an average captain.

However, Lady Haruko, due to her weak reiatsu, couldn't withstand the pressure of Captain Ailin's immense spiritual power. This caused her soul to weaken, and even Captain Unohana was unable to find a cure.

To save Lady Haruko, Captain Ailin sought out former Captain Kisuke Urahara of the Twelfth Division during a mission. Using his overwhelming strength, he forced Urahara to research methods to restore Lady Haruko's health.

This research led to the study of soul 'Hollowfication'... Ultimately, Captain Ailin completed his research and successfully cured Lady Haruko.

Decades ago, Gin informed Captain Hirako about Captain Ailin's research on Shinigami 'Hollowfication.' To investigate the truth, Captain Hirako and others sought out Captain Ailin's former experimental site.

However, to their surprise, the site had been abandoned by Captain Ailin after curing Lady Haruko. Kisuke Urahara took over the research, and as a result, Captain Hirako and the others became his test subjects...

To prevent Urahara from exposing him, Captain Ailin used certain methods to influence the nobles of the Central 46 to order Urahara's immediate arrest. During the arrest, Captain Ailin intervened, displaying his immense power and forcing Urahara to take the blame for the entire incident...

In recent years, although unnoticed by others, I have sensed a growing unease. This unease stems from Captain Kuchiki of the Sixth Division's wife, Hisana Kuchiki.

I had the honor of attending Captain Kuchiki's wedding. The moment I laid eyes on his wife, I knew that Soul Society was likely to face another calamity.

I discovered that Hisana Kuchiki shared a similar condition with Captain Ailin's wife, Haruko Kuchiki. No, it should be said that Hisana Kuchiki's condition is even more severe. Even Haruko Kuchiki possesses some reiatsu. Hisana Kuchiki, however, has absolutely no reiatsu.

Within the Seireitei, filled with immense spiritual pressure, Hisana Kuchiki's lifespan will be even shorter than Haruko Kuchiki's.

To prevent Hisana Kuchiki's soul from weakening and leading to her death, I predict that Captain Ailin will soon resume his 'Hollowfication' experiments.

As the Captain of the Eleventh Division, with Lieutenant Zaraki by his side, Captain Ailin enjoys the most leisure time among all the captains.

He typically spends his days at the Kuchiki Manor, occasionally visiting izakayas. However, in recent years, he has been frequenting the Rukongai almost daily. I suspect he has already begun his experiments.

Therefore, I discreetly investigated the casualty records of all Shinigami within the Gotei 13 and confirmed my suspicions that Captain Ailin has secretly resumed his Hollowfication experiments.

To uncover the truth and learn from the experiences of Captain Hirako and the others, I have documented all my findings here and requested Captain Gin of the Third Division and Captain Tōsen of the Ninth Division to assist me in investigating Captain Ailin.

If we return safely, it will mean that my investigations were mistaken, and I will apologize to Captain Ailin.

However, if we end up like Captain Hirako and the others, becoming Captain Ailin's test subjects, please be wary of Captain Ailin.

Sincerely,

Captain Sōsuke Aizen of the Fifth Division"

"Tsk, tsk..." Ailin couldn't help but admire Aizen's cunning after reading the letter.

The information presented was both logical and well-supported, weaving together unrelated events to form a convincing narrative.

If Ailin hadn't truly been innocent of conducting Hollowfication experiments, even he might have suspected himself as the mastermind behind it all.

However, it was clear that regardless of how much the captains trusted Ailin, this letter would plant seeds of doubt in their minds.

What if everything written in this letter was true?

Would they be the next victims of Captain Ailin's betrayal?

"Captain Ailin, you have read the letter. Do you have anything to say in your defense?" Yamamoto asked, his voice heavy with suspicion.

"Captain-Commander, the contents of this letter are highly suggestive. Even I find it difficult to identify any flaws in its logic," Ailin admitted, shaking his head.

Aizen's move was undeniably a near-perfect "checkmate."

He had the testimony of Ailin's former disciple, Gin Ichimaru, who now lay defeated at Ailin's hands.

He had woven together a logical narrative, connecting Ailin's actions with his own deeds, lending credibility to his claims.

After all, it was true that Ailin had been spending most of his time in the Rukongai in recent years.

Even Ailin knew that revealing his true purpose – searching for a "child" – would only reinforce the credibility of the letter.

"So, Captain Ailin, are you admitting to your actions?" Yamamoto pressed, his eyes opening slightly, his reiatsu surging.

"Hold on, old man. I merely stated that I find it difficult to identify flaws in the letter. I haven't admitted to anything," Ailin countered.

"My presence in the Rukongai these past few years wasn't for Hollowfication experiments. Both Haruko and I have reached the age where we desire to be parents. We've been searching for a child to adopt."

"As for what you see before you... it is clearly Captain Aizen's attempt to frame me. Today, as I was returning to the Seireitei, I sensed a reiatsu unlike that of a Shinigami or a Hollow. When I arrived here, I witnessed Captain Aizen conducting a Hollowfication experiment on a Shinigami.

Upon seeing me, Captain Tōsen attempted to eliminate the Hollowfied Shinigami to destroy the evidence. I intervened.

Then, Captain Aizen began to question me loudly, accusing me of conducting the experiments. It's clear now that those words were intended for you, Captain-Commander, to shift the blame onto me, just as he did with Kisuke Urahara decades ago, making me his scapegoat.

While you were on your way here, Tōsen and Gin attacked me, and I defeated them. And that is what you see before you now."

Despite the seemingly absurd explanation, Yamamoto found himself more inclined to believe Ailin than the letter.

The main reason was that the entire situation felt too convenient, too perfectly orchestrated.