Given Isshin's lazy nature, it wouldn't be strange if he was absent for a day or two. But disappearing for several consecutive days was abnormal. Even with his laid-back, idle character, it was unlikely he'd vanish for so long without a trace.
Usually, even when sneaking out, Isshin would show up at the 10th Division first, find an excuse, then leave. This time, there was no warning, no news… just gone.
Especially when a Captains' Meeting was held during this period, and Isshin neither attended nor sent word, it directly drew Yamamoto's attention. Captains' Meetings were important, and Captains generally attended.
If something urgent prevented attendance, they should have notified Yamamoto. But Isshin did neither… he didn't attend nor send any explanation.
…
1st Division, Duty Room.
Yamamoto was speaking with Toshiro.
"Toshiro, regarding Captain Shiba's whereabouts, do you have any leads?" Yamamoto asked.
"Apologies, Genryusai-sensei. I truly don't know about Captain's whereabouts," Toshiro replied, mustering his Oscar-worthy acting skills.
"Earlier, Captain just said he had something to attend to and left. I thought, as usual, he'd wander around and return. I never expected no news afterwards."
"For the first day or two after his disappearance, our 10th Division didn't pay much attention. While vanishing for a day or two wasn't common, it happened occasionally, so we weren't too concerned."
"But when Captain still hadn't returned, we realized something was wrong. I mobilized the 10th Division's members to search, but found nothing. Then, until you summoned me, there was still no trace."
Honestly, Yamamoto highly valued Toshiro. Deceiving him made Toshiro's conscience ache slightly. Yet, Yamamoto trusted Toshiro completely and harbored no suspicion.
"In that case, return and continue organizing the 10th Division to search for Captain Shiba. I will also order other divisions to assist," Yamamoto said.
"Thank you, Sensei. I'll take my leave," Toshiro nodded.
As Toshiro prepared to leave, Yamamoto suddenly stopped him. "Oh, Toshiro. Since Captain Shiba is absent, you shall temporarily act as Captain and handle 10th Division's affairs."
"Yes, Sensei," Toshiro acknowledged.
Even without Yamamoto's order, Toshiro had been managing the 10th Division. Now, Yamamoto simply gave him the official title.
…
10th Division.
Returning from the 1st Division, Toshiro entered the Captain's office.
"Yo, Toshiro, you're back. What did you tell Captain-Commander about Captain?" Rangiku asked.
"Nothing much. Anyway, I managed to handle Captain-Commander. He'll mobilize the entire Gotei 13 to search for Captain. But I don't think it'll last long. The Gotei 13 can't just focus on finding the Captain and ignore everything else," Toshiro answered.
As Toshiro predicted, events unfolded accordingly.
Yamamoto ordered the entire Gotei 13 to search for Isshin. After half a month, combing the entire Soul Society yielded no results. Reluctantly, the search was called off. The Gotei 13 bore the heavy responsibility of protecting the Soul Society and Seireitei, and they couldn't neglect all duties just to find Isshin.
With the search fruitless, Isshin was officially declared missing.
Since Isshin was missing, he could no longer serve as 10th Division's Captain. Someone else needed to be appointed.
Thus, regarding the 10th Division's captaincy, Yamamoto decreed that each division's Captain could recommend capable Shinigami.
Shinigami from any division who believed themselves capable could also apply for captaincy exams. Upon passing, they could become the 10th Division's Captain.
Although Yamamoto already had a suitable candidate in mind, procedures had to be followed. However, he believed that despite competition, the final Captain would undoubtedly be 'him'.
…
Three Days Later.
Having decided on the 10th Division's captaincy, Yamamoto convened another Captains' Meeting to announce the new captain.
At the 1st Division, Captains, the pinnacle of Shinigami, arrived with their Lieutenants to attend the meeting.
"Yo, Ukitake, you're early today," Kyoraku of the 8th Division greeted his close friend Ukitake at the entrance.
Ukitake smiled. "Yes, I've been feeling better lately, so I walk a bit faster."
"Oh, Jushiro, who do you think the new 10th Division's Captain will be?" Kyoraku asked.
"Haha, you're asking the obvious, Shunsui. Who else is more suitable than 'him'?" Ukitake laughed.
"Well, true enough." With that, they entered the meeting room together.
Captains' Meeting' Room.
Yamamoto stood at the head, with Captains lining both sides.
Yamamoto surveyed the Captains. "Good. All are present except the 10th Division's Captain."
Thump!
Yamamoto tapped his cane. "Then, regarding the 10th Division's captaincy, I won't beat around the bush. I'll announce it directly."
He glanced towards the meeting room entrance. "Enter!"
Creak!
The doors opened. A figure strode in.
Tap, tap, tap...
The figure walked steadily into the center of the gathering and stopped.
The newcomer had silver hair, emerald-green eyes. His slender frame was draped in a Captain's Haori, exuding both composure and authority.
"Everyone, I am the new 10th Division's Captain… Hitsugaya Toshiro!"