The Rebirth In Bleach
Spar

Itsuki took off its load and threw it to the side gently, which still caused the crater to form due to its sheer weight. Yamamoto took off the top of his uniform, revealing his muscular body that was covered in scars.

 His previous weak appearance dissipated as he stood upright like a sword that had been unsheathed. His walking stick floated in front of him as his outer layer peeled off revealing a katana. It had a handle and a purple holster with circular hand protection.

"Let's start this beating, son, take the first step"

Itsuki gets into the position of Iaido as he disappears and reappears next to Yamamoto. Pulling both of his swords he initiated Hiten mitsurugi-ryu, Soryusen (Twin Dragon Flash) but this time with two swords.

Yamamoto blocked the attack and pushed it back before Itsuki could land the second sword. When Itsuki landed, he did not stop there because he was still pushed back gathering dust in the air. He looked up only to see Yamamoto missing.

 Dust cleared around him, he realized that Yamamoto was already beside him slashing with incomparable might. Avoiding Itsuki's sword seeing the sword touching the ground created a crack in the ground.

 As soon as Itsuki's foot touched the ground, he immediately pushed to attack with the memory partition and acceleration of his mind come into play.

With Yamamoto in mind, a series of clashes and strikes followed with the two entering a stalemate.

 The two of them were currently using pure swordsmanship with Yamamoto relying on his years of experience and Itsuki relying on his pure speed and mental abilities.

The deadlock was broken with Yamamoto who had the upper hand as he slashed through Itsuki's protective reiatsu and created a wound on his shoulder which caused him to fly back and land in a rock formation.

Rise back up, Itsuki holds his wound only to see Yamamoto lose his sword and punch him. As the punch came towards him, he realized that it was not as normal as it seemed. Alarm bells sounded for Armageddon in his brain as he quickly dodged to the side.

"Ikk"

Leaving Yamamoto's mouth as his fist landed created a huge depression in front of him. Although Itsuki avoided it, he still bounced from the impact. Also dropping his sword, he entered a bare-handed combat situation with Yamamoto but was soon destroyed. 

Itsuki quickly found a gap and placed his hand in a blocking motion

"Bakudo #39, Enkosen"

A circular disk of revolving energy appeared in front of him as Yamamoto's fist landed on it causing him to be relaunched.

Falling back onto his sword he immediately picked it up and immediately got ready. Yamamoto also took his sword and took it. 

The two looked at each other as their two reiatsu surged. Reiatsu Yamamoto had reached an unprecedented height as he released it while, although, Itsuki was one level lower, it could still be felt increasing. The training ground was unable to accommodate both of their reiatsu as everyone in the soul society sensed it.

Division 8 Headquarters

Shunsui immediately turned around and shed an imaginary tear,

"What happened taichou"

'I'm with you, kouhai'

Division 13 Headquarters

A sickly man was seen lying on a futon as he was being cared for by a servant. He had a head full of white hair that was ponytailed low and black eyebrows with a bony appearance. His face was relatively handsome. Sensing his master's reiatsu, a gentle smile appeared on his face remembering him. His brows suddenly twitched as long-forgotten memories returned.

'Get yourself, Kouhai'

Everyone felt the reiatsu of the captain commander blazing and the small one facing him. While some Shinigami are preparing, there are captains calming them down while giving prayers inwardly to new students. Well most of them, some of them don't even care.

Division 1 Headquarters

If people on the outside can feel the cancelled version of Yamamoto's reiatsu, imagine its heaviest burden befalling Itsuki. Sweat began to pour out on Itsuki, but he still maintained his stance.

"Everything in this world, turned to ashes, Ryujin Jakka"

"Going from above, Ryurai"

"Crackling, Byakko"

The two release their Shikai as the fire begins to spread towards Itsuki. Putting the Byakko in front, it negates Ryujin's fire, but the heat is still there. Bringing Ryurai over Itsuki goes into the same position as he fights against the Hollow as Yamamoto waits for his student's movements. While thrusting the sword in front he shouted,

"Shashitoshi"

The same technique came out as Itsuki was pushed forward towards Yamamoto. Believing his instincts, Yamamoto surprisingly dodged the attack because there was a wound on his chest. Itsuki is not free from punishment as she has a minor burn around her right arm that holds Ryurai. Calling Byakko he muttered,

"Kokyu, Byakko"

Suddenly the sword disappeared and turned into the wind that surrounded Itsuki. A faint shadow of a tiger could be seen appearing on the shield that was now forming. No matter where the fire approached him from the shield, his magic worked and cancelled it. Now holding Ryurai with two hands he attacks Yamamoto, finally showing the essence of Hiten mitsurugi-ryu. 

With regards to Ryujin Jakka, Ryurai did not lose. With the fire put out by the Byakko, the only thing Ryurai struck was a very hot sword. However this does not deter Ryurai as it also heats itself with electricity reaching the same level of heat.

Again, the spars became dependent on their swordsmanship with similar results, but this time it took longer, showing Itsuki's progress in swordsmanship.

This lasted for a while before Itsuki was thrown backwards, inches away from falling unconscious. Sealing back his zanpakuto, Yamamoto ended the spar as Itsuki also re-sealed his. Dismissed, he dragged his beaten body and entered the herbal bath as he fell asleep.

After some time Chojiro comes and finds him sleeping. With a small smile she lifted him up, told him to put on his nightgown and put him in her room. Fortunately Itsuki still wears pants.