Miroku had little doubt how Inuyasha intended to resolve the situation now that his brother had arrived, so he was not particularly shocked when Inuyasha agreed to a duel. It was foolhardy to the extreme, but naturally he wanted to continue testing his reforged sword, and what better target than his hated brother?
The others all demanded to know what Inuyasha thought he was doing, and if he thought he could win, but Miroku held back. As far as he was concerned, the conclusion was foregone. Inuyasha would be soundly and bloodily defeated, but would hopefully still have his life at the end of the fight. Sesshoumaru would sneer and walk away like the entire thing had been beneath him, even though it began at his own instigation. Life would go on.
"Shut up!" Inuyasha interrupted. "It doesn't matter what I want to do. He's not the type of enemy to back down just because I say 'wait'."
Sesshoumaru smirked. "That's right. Come at me, Inuyasha." He lifted Toukijin in challenge. "If you don't, I will."
"I hope you don't regret digging your own grave!" Inuyasha snapped, but he was clearly all bluster. The moment he drew the Tessaiga from its sheath, it was obvious that the sword was still too heavy and cumbersome for him to wield with any skill. With Sesshoumaru in full command of his own blade and his skills as a swordsman, Inuyasha was going to have a very difficult fight ahead of him.
The best he could manage was to get the Tesssaiga in front of him enough to serve as a shield before Sesshoumaru brought Toukijin down upon him. This blocked the physical blow, but cuts still appeared all over Inuyasha's body, his blood flowing freely.
"Just as I suspected, the Tessaiga is losing against Toukijin," Toutousai observed sadly.
"But he blocked!" Kagome protested.
"Does this mean Inuyasha has no chance at all?" Miroku asked.
"Well," Toutousai said, drawing out the word as if to give himself time to think. "He can barely swing the sword. If he had better mastered the sword, he might have a chance. But as things stand…"
Kagome continued her protests, clearly seeking some sort of reassurance from Toutousai, while Miroku turned his attention back to the fight. Strangely, Sesshoumaru had stopped attacking. He merely watched as Inuyasha picked himself back up. Why not press the attack? It must have something to do with whatever Sesshoumaru was trying to test.
"Have you changed your fighting style, Inuyasha? You used to swing that sword wildly all over the place." Sesshoumaru could not have found a better way to goad Inuyasha back into the fight than to ask this question in this manner.
Miroku sighed as Inuyasha screamed, "Shut up!"
The hanyou threw himself at his brother, wielding the Tessaiga with something resembling his former speed and agility, but Sesshoumaru was ready for him. He calmly brought Toukijin around to guard, effortlessly fending off his brother's attack. Inuyasha, on the other hand, was cut by Toukijin's power all over again.
"The Tessaiga has become heavier, hasn't it?" Sesshoumaru observed. "Perhaps if the sword is too much for you, you'd be better off without it." He struck forcefully, tearing the Tessaiga out of Inuyasha's grip and knocking the hanyou to the ground in a bloody heap.
Remembering all too clearly the warning Myouga had given them—that the sword sealed away Inuyasha's youkai blood, and that once begun the transformation would be impossible to stop—and prepared to step in. If Inuyasha refused to use the Tessaiga, someone else would have to put a stop to the fight before it was too late, and Miroku didn't trust Toutousai to intervene the way he had the last time the brothers fought.
Inuyasha clawed his way back to his feet, declared that he did not need a sword to defeat his brother, and went straight back to the fight with nothing but his claws for a weapon. Kagome was screaming at him to stop, that he must use the Tessaiga at any cost, but he paid her no mind. The power of Toukijin threw him back before he could even land a blow. Inuyasha landed on his feet at least, but had been visibly bloodied all over again.
Beside Miroku, Sango watched the fight with the same sort of grim curiosity he was feeling. Just what was Sesshoumaru trying to do, if not kill his brother outright? A moment more and they had their answer.
"So the half-youkai is still only half-youkai," Sesshoumaru observed. Somehow he had known that Inuyasha transformed during the fight with Goshinki, and he had come here to see that for himself as much as to retrieve his new sword. "Enough, then. Die, Inuyasha."
Something in the air changed as he brandished Toukijin for the killing blow. Inuyasha was becoming a full youkai again, Miroku realized. With no way to guarantee that the process would not be permanent this time, he shouted a warning and reached for the prayer beads that bound the kazaana. He didn't like to do it—in fact the mere thought of Toukijin coming anywhere near the cursed hole in his hand would doubtless be enough to give him nightmares—but when the alternative was letting Inuyasha become a full demon or be cut down like a dog…
But Toutousai intervened first. "Grab Inuyasha and run," he advised, already puffing up his cheeks in preparation to blow fire over the battlefield. "I'll catch up momentarily."
As fire burst over the area, Miroku had the unenviable task of knocking some sense into Inuyasha, getting him to retrieve the Tessaiga, and convincing him that now was the time to retreat rather than fight. "We have to get out of here, my friend," he said, hoping that Inuyasha really was still his friend. (No doubt seizing a friend who was losing himself to his own demon blood would only add fuel to the fires of Miroku's nightmares.)
At first Inuyasha did not seem to recognize him, but as he watched Kagome helping Sango with the broken halves of the hiraikotsu, he seemed to snap out of it enough to follow instructions. "Get the Tessaiga and come on, we have to get out of here," Miroku told him. Astonishingly, he did as told.
In the chaos that followed, they were able to make their escape relatively unharmed and begin the search for a safe place to regroup and tend to Inuyasha's injuries. They would have to hope that, having found out whatever it was he wanted to know, Sesshoumaru would leave them be for now.