So I got this idea after re-reading Shunsui's meeting with Tatsuki, Keigo and Mizuiro, how he told them Ichigo might have to stay in Soul Society since his powers could pose a risk to the world of the living.
So what if Ichigo's powers were too strong for him to go back and he had to stay in the Seireitei
Ichigo stood on top of Sōkyoku Hill and looked out over the Seireitei.
"It's gonna take so much time to rebuild it"
He then heard footsteps behind him and turned around to see Shunsui come towards him.
"Head-captain"
"There's no need to be formal when it's just the two of us Ichigo"
"Sorry Shunsui"
The head-captain smirked and stood by Ichigo's side.
"They sure did a lot of damage"
"Yeah. But like Jūshirō would say, we can always rebuild"
"How is he?"
Shunsui looked at Ichigo and saw slight worry in the young man's eyes.
"He's weak but lieutenant Kotetsu says he'll be fine after some rest.
-Suro is with him right now"
Ichigo smiled at hearing that.
"That's good"
"Indeed"
Shunsui then got a serious look on his face.
"Ichigo the reason I came here to find you is because I wanted to tell you something about your powers"
"They're too strong for me to return to the world of the living aren'y they"
"You knew?"
"I overheard Ichibe tell the other members of the Royal Guard about it while I was training with them.
-So I can't go back?"
"I'm afraid so. Your spirit energy would have negative effects on the world of the living.
-But I've already arranged for you to live here in the Seireitei"
"I appreciate that"
"I also wanted to ask if you're interested in joining the Gotei 13."
"Don't I have to go through the academy?"
"Ichigo, your spirit energy is already at the level of a captain and you have great control over it since you trained with the Royal Guard.
-The only thing you need to learn is Kidō which we can arrange for a captain or lieutenant to teach you"
Ichigo looked at him and then out over the Seireitei before turning back to Shunsui.
"I'd be honored to join a division"
"I'm glad to hear it because we do need a new captain for the 7th and 8th division"
"Me, a captain?"
"Like I said, your spirit energy is at that level. But if you'd rather join a division to learn first, then that's fine too"
"May I have some time to think?"
"Of course"
Ichigo smiled and started to walk away.
"And Ichigo"
"Yes"
"Don't worry about your family. I went to the world of the living after the first invasion and informed Isshin as well as your friends about this so they would be ready incase it happened"
"I appreciate that"
"I also gave them Soul Tickets which allows them to visit whenever they want.
-Chad, Orihime and Uryu will also get one each when they leave"
"Thanks"
Ichigo then Flash Stepped away to find his friends.
"Me, a captain of the Gotei 13"
He went around the Seireitei until he found the others.
"Hi guys"
"There you are Ichigo, said Orihie"
"Where have you been, Uryu asked"
"Just up on Sōkyoku Hill"
He then looked around and noticed that a certain blac-haired woman and red-haired man was missing.
"Where is Rukia and Renji?"
"At her divisions, said Chad"
"They're trying to figure out how to rebuild the parts of their barracks that were destroyed, said Orihime"
"I see"
Ichigo looked at the ground and then back at his friends.
"Listen guys, there's something I have to tell you"
"What is it, Chad asked"
"I... I'm not going back to the world of the living with you guys"
"Why?"
"The head-captain told me that my spirit energy is too powerful and if I return, it would have negative effects on the world of the living"
His friends looked at him in surprise before Uryu and Chad's expressions changed to more understanding.
"So you're joining the Gotei 13, said Uryu"
"Yeah. The head-captain wanted me to take one of the empty captain spots"
"Right away, said Orihime"
"Yes. My spirit energy is at the level of a captain and I know Bankai which Yoruichi told me is needed to be a captain"
"What about your family?"
"Shunsui siad he had warned dad ahead of time about this along with Tatsuki and the others. He had also given them something that allows them to visit Seireitei whenever they want.
-You guys are gonna get them as well when you leave"
Orihime was quiet for a moment before looking at him.
"It's gonna be different without you"
"I know but I can't do anything agianst this and you guys can visit whenever you want.
-I also count on you guys to help defend Karakura Town since I won't be around"
The three looked at each other and nodded.
"You can count on us Ichigo, said Chad"
"Indeed, said Uryu"
"Thanks guys"
Rukia and Renji then appeared.
"Oh Renji, Rukia, said Orihime"
"We though you had to look over your divisions, said Uryu"
"Katsurou came and took over so I could take a break"
"And the captain let me have a break too"
"Did you two know about Ichigo, Chad asked"
"Knew what about him?"
"That my powers are too strong for me to go back to the world of the living"
"Oh yeah we knew"
"Ichibe warned us, said Rukia
-But you guys don't need to worry, Renji and I will make sure he behaves"
"What's that supposed to mean Rukia, said Ichigo
-Incase you don't know, I've been offered a captian position which means I'll be of higher rank than you two"
"You're not a captain yet which means I can still treat you the same as always"
The other four just looked at them and couldn't help but laugh.
"Well things won't be boring around here that's for sure, said Renji"
"I'm just worried that when Kenpachi finds out, he'll come after me every day, said Ichigo"
"I'm sure the head-captain will give him a warning so he won't do that, said Rukia
-Can't have him chase a new captain around"
"Which division are taking over by the way, Uryu asked"
"Either the 7th or the 8th, said Ichigo"
"Well the 7th is made up of people who are sincere and unpretentious, said Renji
-Captain Komamura and Tetsuzaemon both believe strongly in moral obligation and compassion"
"And the 8th is a bit serious due to lieutenant Ise but they were also a bit relaxed due to captain Kyōraku since he usualy said only female Soul Reapers could join, said Rukia
-That's what captain Ukitake has told me at least. After Nanao became the lieutenant, it became more strict with certain things especially drinking"
"Wouldn't surprise me if Tatsufusa has let go a bit of that seriousness since Kyōraku was promoted to head-captain and left the division in his hands
-That and his big ego"
Ichigo scratched the back of his head at hearing that.
"Maybe the head-captain should try and make Lisa the captain of the 8th, she's good at making people listen to her"
"So you'll take the 7th then, Rukia asked"
"Maybe, your desriptions of the divisions did help but I'll have to think a bit more before telling the head-captain about my decision"
Later that day.
Ichigo made his way to the 1st division and entered Shunsui's office.
"Ah Ichigo, have you made a decision?"
"Yes. I talked to Renji and Rukia earlier today and they explained what the divisions were like.
-It helped me a bit in making my decision of which to join"
He then got down on one knee and bowed his head.
"I've decided to take the place of the 7th division captain"