Both fighters clashed horribly. As determined as Ichigo was to save Rukia, Renji was as determined to not allow him. Their opposing wills became a battle of strength, grit, tears, and blood.
Ichigo held the upper hand in sheer power, and was able to drive Renji into a corner, but he squirmed free, and utilizing his advantage in agility, was able to slash his enemy with weaker but numerous and thorough small cuts that eventually combined to take their toll.
Ichigo was leaning on Zangetsu for support and appeared unable to defend against another attack, but as Renji towered above him to deliver a final blow, he was blocked, and forced away with an impossible outburst of power from both the mind and body. Ichigo shouldn't even be able to stand anymore, from all the wounds he had received during the battle, but he stood anyway, and continued fighting, because he would not forgive himself for falling.
"Is that all you got?" Ichigo laughed painfully with feigned confidence.
"I haven't shown you everything," Renji pounded back. "Let me tell you: a proper shinigami seals his zanpakuto to save energy. It's obvious that you, a shinigami who got his powers by mistake, can't control your spiritual energy. Your sword may be big, but it's out of control. I'll show you the result of years of training and mastery! Howl, Zabimaru!"
His zanpakuto transformed into a snake creature, with separating scales and a curving steel body. It winded in the air, becoming more difficult to avoid, as it spun around Ichigo's guards and nicked his shoulders and ankles. Renji then commanded his sword into a direct blow; Ichigo blocked it, causing a shattering ricochet. Ichigo tumbled, but Zabimaru seemed to absorb the blow for his owner, nearly tangling as Renji's hand, choking the hilt tightly, merely shook from the shock.
Renji attacked again, twirling Zabimaru about him, leaving no space for Ichigo to pass. The spinning blade destroyed the surroundings, the remains of his home, Rukongai, but no longer his home. Broken pieces of wood became smaller broken pieces of wood and shattered pieces of glass became finer shattered pieces of glass. The teddy bear, Mamoriko, still smiled as it was shredded and its white stuffing floated among the air.
Ichigo concentrated not on Renji, but his blade, remembering that as Urahara had taught him, in a tough battle, the opponent would attack using a combo with the highest possible amount of hits, and if all parts of the combo could be avoided, then a sure opening would reveal itself.
Ichigo concentrated on the blade, recognizing that its limit was three consecutive strikes. He dodged the first curve, the second curve, the third curve, and rushed into the opening, but there was a fourth curve. Renji grinned, twisting his hand his grip on the hilt, causing Zabimaru to contort, twist and bend in a manner impossible for any living being, but Renji made it possible, forced it possible. Zabimaru curved, and struck Ichigo from behind, driving into his flesh, but missing the vital spinal cord narrowly as a result of the difficult and convoluted curves it had to travel to reach that point.
Renji recalled his blade and laughed, "This is what years of training will do. This is mastery. Zabimaru may have a limit of three strikes, but I have no such limit. A fourth curve is not impossible for a wielder like myself."
"Limits are meant to warn us," Ichigo panted. "If we surpass them, then we take grave and severe risks, with consequences that may leave scars that will never never disappear."
"We can surpass our limits, if we force ourselves and train. I trained all these years, in the hopes that a clan might adopt me so that I would once again be beside Rukia. To prove myself, I broke the limits."
"Your zanpakuto, was not ready to pass its limit."
"The zanpakuto share the same will as its wielder. All shinigami know this."
"No. Zanpakuto have their own will, separate from the wielder." Ichigo spoke, as though there were another voice inside of him. "A zanpakuto depends on the owner to save him from purgatory and regret. Only then, is its full potential reached. Unless I save Rukia, my zanpakuto will continue to regret and wallow; therefore, I will save her, and first I will defeat you. I will pass a limit, that is too far for you to even see."
Once again, Zangetsu began to glow pink, pulsing with energy. "What is this?" Renji thought frantically. "Where is it getting its power from?" He didn't care, and readied his zanpakuto for another strike. He had to win. He had to do it. Zabimaru howled, in pain, as it met a much stronger opponent in Zangetsu. This time, the pain carried through Zabimaru's body and reached Renji. Both clattered to the ground.
Renji was a man of shattered hope, in shock, in disbelief. "How? Why?" were the only words he could think of.
"A zanpakuto grows stronger when it responds to the feelings of the wielder. You claim that you fight for Rukia, but you think only of your own feelings, not of hers, nor of your blade. You may think of thought and feeling, but they are empty, if they are not for someone else. Both Zangetsu and I wish to save Rukia; therefore, no one will stop us."
Ichigo continued his stride to the south gate, past a broken man, with a broken sword.