Sonic didn't have to wait long. After only a couple minutes he felt a surge of reiatsu from the cave before a column of light erupted from the mountainside. The column swung down, cutting clean through the rock and sending a torrent of water towards Sonic. The hedgehog jumped up to land on a tree branch as the wave swept across the clearing, uprooting many of the trees in the process.
"That sword really is something else," he admitted with a low whistle, jumping down to the ground. "And I'm willing to bet that's just from drawing it." He looked to where the waterfall had been and yelled, "So you comin' outta there or what? I'm dyin' of old age out here."
A wave of golden energy came blazing at him and Sonic quickly jumped out of the way. The wave carved a path of destruction for almost a hundred meters before dissipating. Sonic gave a nervous chuckle as he looked at the sheer power Gilgamesh now commanded.
"Aside from the regret you're now feeling I'm curious to know why you allowed me to obtain the sword," Gilgamesh asked as he walked into the clearing. He easily held the claymore in one hand and the katana in the other while his cloak now glimmered with a golden aura.
"To prove a point and end this damn grudge you have with me," Sonic answered simply.
Gilgamesh let loose an uproarious laugh. "What point could you hope to prove? That you can only defeat me after nearly dying?" the human asked him. "I fully control both of these blades. There won't be a repeat of what happened with Muramasa, of that you can be assured." He brought the katana back and swung, letting loose a wave of pure white. With a single swing Sonic split the wave and ran at Gilgamesh.
Any doubts Sonic had about the human's strength were wiped away as he deftly blocked and parried Sonic's attacks with both blades. Gilgamesh swiped at Sonic with Excalibur only to have the hedgehog land on the blade and vault into the air. He spun once the face the human and then rocketed towards him with shunpo. Gilgamesh crouched and leapt towards him. Their blades met and Gilgamesh used his free hand for another swing. Sonic blocked with his right leg and the blade bounced harmlessly off the prosthetic. The human's eyes widened in realization as they landed and Sonic began using his sheath as a blade. Gilgamesh batted away the blunt instrument only for Sonic to score a small cut on his cheek. With a growl he pulled Sonic into a bear hug and wrapped his arms around the hedgehog's torso, squeezing tighter and tighter.
"I'd like to see you get out of this one," the human mocked him.
Smiling through the pain Sonic replied, "Your wish is my command." Kaiyō Mujō's sheath tapped Gilgamesh's chin and the human scoffed. Sonic then drove his knee into his hand, slamming the sheath into the human's chin and throwing him upward. Sonic jumped up and planted his right knee into Gilgamesh's back before bringing his hands down together into his stomach. Gilgamesh crashed into the ground, his entire body wracked in pain. "You know what they say," Sonic told him with a smirk. "Be careful what you wish for."
"You missed your chance to strike me down," Gilgamesh pointed out as he struggled to his feet. "Are you sure that was wise?"
"Too easy," was the hedgehog's response. "When I beat you I want you to know there was absolutely nothing you could have done to stop it."
The human gripped the katana tightly as he slid Excalibur into his robes. "I will make you regret those words. Fuzen, Yawarakai-Te!" Two sets of pure white wings extended from Gilgamesh's back but the blade remained unchanged. As his wings flapped Gilgamesh rose gracefully into the air. "Well? What do you think of your master's sword?"
"Looks a bit different than what I was expecting," Sonic admitted and Gilgamesh shot him a curious glance. "What? You thought the old man would just forget to mention that you took his sword?" He then let out an exasperated sigh. "Who am I kidding? Of course he would forget. Guess I got lucky this time." Sonic swung his sword once and, without a word, released his katana fuzen. "Too bad you only got half of it."
"We'll see about that." Gilgamesh let loose with a white wave that Sonic split with ease. As he did Gilgamesh appeared behind him in the blink of an eye and made a thrust towards Sonic's heart. The hedgehog batted the blade aside and swung down, releasing a ryūkai tsume. With a twist of his wrist Gilgamesh blocked it, covering him in a spray of water. Sonic jumped back and let loose with three more that the human blocked with his wings.
"Onikiba," Sonic growled as he clawed downward. Rather than cutting into him the water droplets forced Gilgamesh to the ground but left him otherwise unharmed. "Well, that's a first."
"I thought it was strange I was suddenly wet," Gilgamesh told him as he shook off most of the water. "Thankfully this blade significantly raises my defenses. I have to ask: what happened to that gauntlet of yours?" His hand wandered over the scar on his face. "I never did get to see what it could really do."
"Ah, what the hell," Sonic replied as he focused his energy. "Seems only fair since you've got those wings now." The katana melted into a blob of energy that wrapped around his right forearm. Once it solidified the blade extended past his hand while a defensive edge formed past his elbow. He charged at the human only to have his first assault blocked by the wings. Sonic dashed behind him and scored a hit on his lower back before being batted away by the wings. Sonic landed on his feet and dropped to place his left hand on the ground, kicking off once he saw the whites of Gilgamesh's eyes. With the first strike blocked Sonic used the momentum to lift himself into the air and spun around for another strike. Gilgamesh dropped to a single knee from the sheer force of the attack but otherwise held his ground.
"There's something different about you," he commented as he saw the animalistic fury in Sonic's eyes. "I almost feel like I'm sparring with Enkidu." He pulled back his left wings and was about to drive them into Sonic's chest when he felt a searing pain from them. He looked over to see the wings on the ground with wisps of energy coming out of where they'd been severed by the blade on Sonic's left arm.
"Maybe I should've mentioned this sooner," Sonic told him with a grin, "but Kaiyō Mujō has two blades. I'm still not used to using both but that doesn't mean I can't." With a twist of his arm Sonic threw Gilgamesh's sword arm back and slashed with both arms, sending up an X-shaped blood spray from his chest. The human swatted Sonic away with his remaining wings as he grimaced through the pain.
"What the hell?" he snarled as he struggled to stand. "How could you have gotten so much stronger in a matter of months?"
"I had good teachers," Sonic replied as the gauntlets reverted to katanas. "And besides, I'm still getting warmed up." He took a deep breath and exhaled slowly as fog started to raise around the two of them. Sonic took several more breaths and in a few moments the clearing was filled with a thick fog.
Gilgamesh looked around as his wings began to regrow. He couldn't see more than a couple feet in front of him but was comforted by the fact that Sonic couldn't either. At least he believed that until something fast and blunt slammed into his ribcage. As he doubled over another attack hit his knee and forced him down. He looked up only to have one more crash down onto his collar bone. "What is this?" he asked between pained breaths.
"Kijokiri no mai," Kaiyō Mujō replied as Sonic held his ribcage. "It means, 'Dance of the Siren Fog'. This is a two-part technique but for most opponents this will be as far as you need to go."
"No kidding," the Guardian replied as he stood up. "So why am I not being chopped up?"
"Because I'm choosing not to," the sword spirit replied, her voice coming from behind Sonic. He responded by spinning to block only to have the blade slam into the back of his knee. "The hell?!"
"Do you not know what a siren is?" Kaiyō Mujō asked, her silhouette appearing in front of him. "Just because you think you know where I am doesn't mean I'm really there. Don't listen to my voice."
"I've been trying to do that all day," Sonic muttered as he closed his eyes. He couldn't properly sense in the fog. It felt like Kaiyō Mujō's presence was all around him. A siren distracts with her song, he thought. Her voice and reiatsu obviously won't get me anywhere and her blade doesn't cut me. Still hurts like hell, though. A whistling from above him caught his attention and he moved to block only for the strike to hit him in the groin, eliciting a high-pitched whine from him.
"This is a non-lethal technique meant to quickly wear down your opponent," she explained to him as Sonic curled into the fetal position. "The downside is that it will also drain your strength from you at a frightening rate. The fog can be created from nearby water and save you some energy but you will still need to blend your reiatsu into it for it to have the proper disorienting effect."
"What's the other part?" Sonic asked. "You know what, never mind. This is bad enough."
"The second part is guaranteed to kill." He opened his eyes as the fog around them faded away. "The moment your blade draws blood in the fog you will activate it. Unless you are left with no other choice I would prefer you not use it. This technique is dangerous enough as it is."
"I'll make sure to remember that," Sonic told her as she began to fade away. It was everything he could do to stand up straight but once he did looked at the sword. There was something about the technique he knew was essential otherwise she wouldn't have shown it to him. He closed his eyes, took a deep breath and exhaled slowly. He could feel his katsuryoku pouring out of him with surprising speed but the fog was almost as thick as Kaiyō Mujō had made it. He kept letting it out until he felt something from inside Kaiyō Mujō. In his mind he could see a pinpoint of light that was rapidly approaching the more energy he expelled. Just as he wrapped his mind around the light he dropped to his knees and fell over unconscious.
"So what do you think?" Sonic's voice said as it cut through the fog. "I know from experience that this one hurts like hell. And it's just as irritating."
"Where are you? How can you see me in all this?" the human asked him as he looked around. He heard Sonic's blade whistling towards his right wings and raised them to block only to feel the blade strike the other side of his collar bone. Gilgamesh cried out in pain as another blade connected with his right arm, nearly breaking the bone.
"Quit holding back and I'll stop," Sonic told him as the human spun around. "Show me what Excalibur is capable of and I'll return the favor in kind."
"You want to see its power?" the human snarl, drawing the claymore from within his cloak. "Then I will show you its absolute power! Fuzen, Excalibur!"
A pillar of golden light shot into the sky, blowing away the fog Sonic had created and enveloping Gilgamesh. Sonic watched as Yawarakai-Te vanished but the wings remained, the tops covered in gleaming armor. When the pillar of light faded away it revealed a Gilgamesh in golden plate armor from head to toe. The joints and one shoulder flared out while the other shoulder was replaced by an azure jewel. The mask of the helmet revealed only his nose and eyes, much like his cloak, and a ribbon of blue hair extended back from the top of his head. The sword itself had transformed into a zweihänder, its guard now a sun with its rays extending out past the width of the blade.
"Now that's more like it!" Sonic said with a laugh as he reformed both of his gauntlets. He could feel Gilgamesh's reiatsu trying to crush him but the hedgehog brushed it off as he charged him. The human blocked with free arm while parrying Sonic's attack with his blade, throwing the hedgehog past him. Sonic flipped around only to see Gilgamesh vanish. Knowing where he'd attack from Sonic turned only to be hit by the flat of Excalibur, flinging him across the clearing. Sonic dug his heels in, tearing up the ground as he finally came to a stop. "You're fast," he admitted. "A lot faster than I expected wearing all that armor. You could have done some serious harm with that last swing."
"Didn't you say something about 'returning the favor' if I showed you Excalibur's strength?" Gilgamesh replied. "You're still holding back, I can feel it."
"You've hit me once. I don't call that showing off," Sonic said as he dropped into an attack stance. "Now come on. Show me what you can do with that oversized hunk of metal!"
Sonic charged once more but just before he reached Gilgamesh he jumped and spun, using his momentum to increase his striking power. The swordsman blocked the attacks easily and grabbed Sonic's throat before ramming his knee into the gut. Releasing him, Gilgamesh spun and lashed out with Excalibur, his blade shattering the gauntlet Sonic blocked with. The force of the blow threw Sonic against the mountainside with enough force to crack the stone. Sonic didn't even see him move as the blade pierced the rock, dissolving Sonic into a cloud of mist.
"Kinda glad I played it safe with that," Gilgamesh heard from behind him. He turned to see Sonic standing there no worse for wear even though his left gauntlet was still missing. "Sorry, I know it was a cheap trick but I wanted to know what I was up against before deciding whether or not it's worth going all-out. I'll say this: You sure don't hold back. If I hadn't made a double then I'd be in some serious pain right now."
"It's understandable if you don't want to fight me," Gilgamesh replied as he removed Excalibur from the stone. "Despite how much you brag you don't even come close to Arias' level. Even with this I still wouldn't stand a chance."
"Is that so?" Sonic said with a laugh. "Guess that leaves me with no choice then. To be totally honest I've been itching to use this ever since I learned how. You'll be my first real opponent with it." Gilgamesh narrowed his eyes in disappointment as fog began to form around them.
"This again?" he asked. He was going to continue until he noticed the fog was rising as fast as it appeared. "Just how much of this do you plan on making?"
"It's actually a side effect of my training," Sonic admitted as his katsuryoku continued to pour out. "If I had done this the traditional manner then I'd just go from one to the other. But since I rushed it I just need to deal with it." Another moment and Sonic could feel the warmth from Kaiyō Mujō's inner light. His remaining gauntlet reverted back into a katana and another formed in his left hand. Gilgamesh couldn't help but stare at the cloud of energy above them as rain began to fall.
"What the hell did you do?" he asked as it started to come down harder. "What kind of attack is this?"
"This isn't an attack," Sonic told him as his expression hardened. "This is me not holding back." He held both Kaiyō Mujōs together at the hilt as he began to glow with an azure light.
"Zenki, Ryūmi Nyotei (Complete Form, Sea Dragon Empress)."