It must be understood that Yoruichi possesses Shunko, which is equivalent to Bankai. She frequently uses Shunko yet never uses Bankai. This might be because Kubo never thought up Yoruichi's Bankai, but that does not mean she cannot use Bankai.
At the same time, Isshin is the same.
A Captain fighting an enemy without even using Bankai, what kind of fight is that?
So, reasoning backward, these people may have long since planned how Ichigo was going to be used.
"Cough-"
Having been exposed so easily by Ichigo, Isshin felt a bit awkward.
"Alright, you saw through it. In fact, I did hold back my strength, because I need to assist you in completing a training session!
"Ichigo, you have always been our greatest trump card!!"
As he spoke, a mysterious look appeared on Isshin's bearded face.
"Ichigo, do you know about the Final Getsuga Tensho?"
"The Final Getsuga Tensho?" A perfectly timed trace of surprise appeared on Ichigo's face.
"Yes, the Final Getsuga Tensho. That is the ultimate secret technique our family relies on!"
"Go. Right here, go and ask your Zangetsu what the Final Getsuga Tensho is!"
"Here?" Looking at the Dangai, Ichigo was very puzzled and knowingly asked again, "Can you train in the Dangai too?"
"Yes!" Isshin nodded.
"The so-called Dangai is a passage completely separated from the space and time of Soul Society and the Living World. The flow of time here is independent!"
"That is why the Kototsu exists, to prevent people from staying here for too long and causing temporal chaos.
"But now, the Kototsu seems to have been destroyed for some reason!"
"From the traces of Reiatsu, Aizen seems to have done something to it!"
"Then if the Kototsu is gone, will that be troublesome?" Ichigo asked again, effectively playing the straight man.
"Yes, or rather, it would originally be very troublesome, because the time density in the Dangai is two thousand times that of the outside world!" Isshin said.
"In other words, one year outside equals two thousand years here!
"At the same time, this place is not only the Dangai, but also a place of exile!
"Anyone banished into the Dangai will be wrapped by the Koryu and will never be able to leave!
"Ordinary Shinigami cannot stop the Kototsu, but there are ways to block the Koryu!"
As he spoke, Isshin took out a string-bound object, swung it out, and fixed it onto the wall of the Dangai!
"This is called Realm Boundary Fixation!" Isshin explained.
"Normally it requires dozens of Shinigami to activate it, but for me, alone is enough!
"The time flow in the Dangai is two thousand times that of the outside world. That means training here for two thousand hours only costs one hour outside.
"Now that the Kotsu has disappeared, this is our opportunity!"
"Ichigo, you will have two thousand hours, about three months, to train the Final Getsuga Tensho!
"Alright, sit down and begin Zanzen!"
"Just be careful. Zanpakuto are usually unwilling to tell their masters about the Final Getsuga Tensho."
"Back then, my Engetsu made a huge fuss for quite a while!"
As if recalling some painful memory, a rather ill-intentioned smile appeared on Isshin's face.
Back then, his Engetsu had caused trouble for so long. He wondered what would happen on Ichigo's side.
"But Ichigo, I believe in you! Go take action!!"
After saying that, Isshin patted Ichigo on the shoulder and sat down to maintain the Realm Boundary Fixation.
"Alright! I'll try to come out as soon as possible!"
Ichigo nodded, closed his eyes, placed Tensa Zangetsu across his legs, and sat cross-legged.
He focused his mind, calmed his breathing, and let his consciousness sink deep into the blade, like diving underwater!
In the next moment, a sensation of falling arrived, and Ichigo once again entered his Inner World.
The young Zangetsu, or rather Tensa Zangetsu, and Ruyi were standing together, staring at him.
Seeing Ichigo, Ruyi smiled brightly and greeted him, while Tensa Zangetsu remained expressionless.
"Wait, what's going on here?"
"Why are you two standing together?" Ichigo asked in confusion.
Ever since the forced three-way balance, the relationship between Zangetsu and Ruyi had not been very good.
"I called her here,"
Zangetsu replied calmly.
"I heard everything Kurosaki Isshin said!"
"We know your purpose!"
"Oh?" Hearing this, Ichigo's eyes lit up.
"If that's the case, then Zangetsu, are you going to tell me? What exactly is the Final Getsuga Tensho?"
As he spoke, Ichigo found it very strange.
Was it really because he was too strong, and this time even Zangetsu had no objections to him mastering the Final Getsuga Tensho?
"No, Ichigo!" Zangetsu shook his head, his expression cold.
"I've told you before, we only care about your life alone. Everyone else in the outside world has nothing to do with us!
"But Ichigo, we also understand you very well. Even if we don't give you the Final Getsuga Tensho, as long as you persist, we won't be able to stop you."
"So, I brought her here!!
"Ichigo, we only have one condition!"
"The Final Getsuga Tensho cannot be given by us alone. She has to give it too!"
Zangetsu said.
The so-called Final Getsuga Tensho is when the Zanpakuto hands over its authority, abilities, everything it has, entirely to its host, allowing the host to instantly reach the highest level the Zanpakuto's power can achieve through training.
In this state, a Zanpakuto that originally possessed its own soul completely shifts from being an independent existence to truly becoming nothing more than a blade in the host's hand.
Because in the most extreme circumstances, the host can expend all of the Zanpakuto's power in a single battle!
That is the meaning of 'final'!
Such consumption cannot be recovered!
Which means that for Zangetsu and the others, once the Final Getsuga Tensho is activated, Zangetsu will have to bid farewell to Ichigo forever.
The problem is that if Zangetsu bids farewell to Ichigo, Ichigo would still have Ruyi to use.
This was something they, who only cared about their master, could not accept.
Why do you get to stay, while I cannot?
That was why Zangetsu proposed this condition!
I know you are strong. You want the Final Getsuga Tensho, okay, no problem, I'll agree to it!
But it can't be just me agreeing to it. Everyone has to agree together!
"Alright, I agree!"
Understanding Zangetsu's meaning, Ichigo could not help but laugh and cry.
'What kind of jealousy contest was this?'
Then Ichigo looked at Ruyi. "What about you?"
Because she arrived a bit later, Ruyi did not have the same level of trust in Ichigo as Zangetsu did.