DISCLAIMER: I do not own Devil May Cry or Bleach.
Nero's fist landed solidly on the jaw of a Soul Reaper, knocking the man out. Nero then started to advance, when there was a flash of movement, and a man with a dark brown pony tail covered by a sedge hat appeared before him. Nero readied the Red Queen.
"Get outta my way!"
The man smiled pleasantly. "No need for hostility. I don't suppose I could convince you to leave?"
Nero snarled, swinging his fist at the man, growing it to a massive size so as to hit the man over the distance. The wall behind the man was crushed, but then Nero realised the man was now standing behind him, drinking from a flask.
"That's an impressive ability you have. Are you sure you won't just join me for a drink?"
Nero turned to face the man, swinging his sword at him, watching in horror as the Red Queen bounced harmlessly off the man's chest. Nero then put the Red Queen away, readying Yamato.
"Come on. Can't you lighten up? You could at least tell me your name?"
"Nero. Now get outta my way or I'll kick your ass outta the way. Kyrie's waiting for me."
"Shunsui Kyoraku is my name. If Kyrie's the girl with the red hair, she should be helped soon. She got into trouble with an Arrancar, and Ulquiorra took her in along with Orihime. I'm sorry, but I can't let you get involved when this matter is so delicate. I promise you the others will save her, but you getting involved will make this more dangerous for her and for us."
Screaming with rage, Nero attacked Shunsui with Yamato, but Shunsui casually avoided the strikes, before pulling his own swords and attacking Nero. Nero slammed Yamato repeatedly against Shunsui's two released Zanpakutos, but Shunsui was casually defending himself. Finally, Shunsui and Nero locked blades, and the two leaned over to regard each other closely, Nero snarling with rage, Shunsui calm and passive.
"Seriously, kid. Just leave. Or calm down. You gain nothing from attacking me like this. I'm not your enemy."
Nero glared at Shunsui. "You ARE my enemy. Anyone who stands between me and Kyrie when Kyrie needs my help is my enemy. Now stand back or I'll kill you!"
His strength far superior to Shunsui's, Nero sent the Soul Reaper captain flying up into the air, before preparing to follow up with a magic attack with Yamato which would destroy Shunsui midair. To Nero's surprise, Shunsui vanished from the air, and appeared behind Nero, slashing Nero straight through the chest.
Nero cried out and fell onto his knees, but then jumped back up and kept attacking. Shunsui defended himself from Nero's rapid, wild strikes, easily predicting his attacks, but finding his strength difficult to counter. Finally, Shunsui parried one of Nero's wild strikes, sending Nero off balance. Shunsui then went on the offensive, slashing Nero repeatedly, before releasing a burst of spiritual pressure, which threw the exhausted Nero onto his back.
As Nero stood, Shunsui sighed. "Well, it can't be helped."
Nero charged, but Shunsui jumped above him. "Takaoni."
Shunsui slammed into Nero, his two swords grinding against Yamato. Nero fell down onto the ground, suddenly unable to force Shunsui away. As Nero hit the ground, Shunsui suddenly flung his sword at the ground in front of Nero, saying, "Kageoni" just as it hit. Nero cried out as a blade suddenly appeared from the ground and stabbed into his foot.
Nero swung the Devil Bringer at Shunsui, but Shunsui jumped into the air. "Takaoni."
Shunsui then slammed his swords into Nero's arm, bearing down on him. Screaming, Nero activated his Devil Trigger, and the phantom creature appeared behind him, attacking Shunsui from above and locking blades with him. For the first time, Shunsui seemed nervous, and he was losing to the phantom. He quickly lowered one blade, holding off the phantom with one sword and holding the other loosely over the ground. "Kageoni."
Shunsui dropped the sword onto the knee of Nero's shadow, and Nero screamed again as a blade stabbed through his foot and up to his knee.
Nero then suddenly gripped Shunsui, throwing him a good hundred metres. Shunsui landed on his feet, having already reclaimed his second sword. Nero was uncertain as to what he was doing, but Nero had noticed that Shunsui had said "Takaoni" every time he attacked from the air, that Shunsui had been stronger even though Nero knew he was the stronger of the two, and that Shunsui had suddenly been on the losing end when the phantom attacked him from above. Nero gathered that Takaoni was an attack designed for attacking from above. Nero also noticed that Shunsui had been weaker when attacked from above than he had originally. With this, Nero understood Takaoni.
Sensing Nero's thought process, Shunsui decided to change his tactics. In a flash, he stood in front of Nero, and slammed his swords into the ground in front of Nero. "Kageoni."
Nero jumped, and watched as two blades appeared where his feet had been. Nero suspected Kageoni was an attack that brought blades from the ground, but he had noticed Shunsui had aimed for his shadow. As a test, Nero rapidly fired a blade beam from Yamato at Shunsui's shadow, and Shunsui jumped aside, his kimono shredding in midair. Nero now understood both of Shunsui's tricks.
Shunsui landed on the ground again. Nero had figured out the tricks Shunsui had used. Nero was something of a berserker, but he was not stupid. Shunsui knew that continuing to use Kageoni when Nero had the blade beams and the expanding arm would be a bad idea, and with Nero possessing the demonic phantom that hovered above him, Takaoni would be considerably less useful too. Shunsui knew he still held the advantage in speed and skill, and he also had one final trick remaining.
Shunsui dashed over to Nero, slashing him, before saying, "Irooni, blue."
Shunsui slashed Nero across the side, but the cut was only shallow. Nero jumped back, before noticing the injury. Nero instantly pieced together what Shunsui had done, but he didn't understand why the cut was so shallow. Shunsui then stepped back, shrugging.
"Your turn."
Nero quickly pieced together what to do, and charged. "Pink!"
Nero slashed Shunsui straight across the back with Yamato, dealing a blow that would normally cleave Shunsui in half, but it only cut a shallow nick across his back. Shunsui suddenly spun around, shedding his damaged kimono. "Black."
Shunsui cut Nero across the leather straps that held his sword to his back, and the cut delved straight into Nero's leg. Nero screamed with both rage and pain, before charging angrily, screaming. Shunsui allowed the strikes to hit him, but they didn't damage him.
"You need to say a colour."
Nero gripped Shunsui. "Black!" He snarled, slashing Shunsui across the chest, another blow that would normally cleave Shunsui in half, but in this instance only gave him a shallow cut. Shunsui instantly dashed forward, spreading his own blood across his chest and back. "Red."
Shunsui slashed Nero in the red vest, cutting him very deeply. Nero screamed with rage, before suddenly declaring, "Red!" Nero swung Yamato at Shunsui, but Shunsui side stepped, allowing the blade to cut him lightly in one of the blood splatters on his left shoulder.
Shunsui then jumped back, considering his options. Nero had figured out that he could only cut the colour he called, but not the part about it doing more damage if that colour posed a threat to him. However, Nero seemed to suspect, or maybe he was merely trying out colours to see what worked. Either way, Shunsui now knew that Nero could survive cuts that would kill even the strongest Soul Reaper. However, Shunsui had a final trick up his sleeve. "Takaoni."
Shunsui appeared above Nero, slamming him against the building behind him. As Nero started to push forward, Shunsui saw his chance. "Kageoni."
Shunsui slammed one of his swords into the building where Nero's shadow was cast, and in an instant, a blade jutted from the building and stuck itself into the back of Nero's neck. Shunsui then jumped into the air again. "Takaoni."
Shunsui slammed into Nero and shoved him through the building and out the other side. Shunsui then caught up to Nero, slamming him to the ground. "Kageoni."
Shunsui stuck his sword into Nero and the ground under him, causing a blade to come from the ground as well, impaling Nero twice. Shunsui then withdrew his sword and kicked Nero into the air. "Irooni, black."
Shunsui jumped up and slashed Nero, who was now covered with several large pieces of the road, which was black. Shunsui still wore only his black robe, having shed his white one and his pink one. The cut was very deep in Nero's torso, and he cried out, being launched back to the ground.
Shunsui dropped to the ground next to a panting Nero and powered down his Zanpakutos, sheathing the two sealed blades. He then took a moment to think on the fight as he stood over his barely conscious opponent.
"You have a lot of power. I've never met anyone with that much brute strength, and even the Arrancar aren't as durable as you. I'm very impressed that you have no wounds at all after all that. Regeneration, am I right? If I hadn't taken you seriously, this may have been a real problem. As it was, you came pretty close to killing me."
Nero rolled onto his back, looking up. "I lost…"
Shunsui shrugged. "Relax. Ichigo will save your girlfriend. In fact, we sent several captains in a while back, so she'll be fine. You should join us in the battle against Aizen and the Espada. You might get to fight the one who actually took your girlfriend."
As Nero slowly nodded, Shunsui said one last thing.
"And don't worry. When they bring your girlfriend back to you, I won't tell her about this."
Shunsui chuckled as Nero raised his glowing middle finger to him, enlarging the arm so that Shunsui had a six-foot long middle finger directed at him.
Analysis:
Nero's fighting style revolves almost totally around sheer force, with little thought of technique. Shunsui is a strategic fighter, and a wild fighting style like Nero's would never beat Shunsui, even though Nero is physically stronger and more durable.
As a minor point, the only weapons Nero has that can actually harm a Soul Reaper are Yamato and Devil Bringer, the Red Queen being a normal sword. Some form of supernatural blade is required to cut a Soul Reaper. Nero holds several physical advantages, but unlike Dante, who has defeated numerous powerful enemies, some comparable to high level Marvel characters, Nero's largest victory is against Sanctus, and he stands substantially lower in power.
Most importantly, Nero has a tendency to lose control of his rage during battle, which almost always leads to him making mistakes. He also only focuses on one thing and charges at it, leaving him open to anything unexpected. This happens with Dante, Sanctus, Agnus and even Echidna. Nero frequently makes mistakes due to his narrow mindset and lack of control. A clever fighter like Shunsui would take advantage of this.
While Nero would be able to adapt somewhat to Shunsui's various tricks, since he has solved several puzzles, and his phantom Devil Trigger would make Takaoni less effective, and he can adapt a little bit, he only has a short history of such fights, and his abilities mainly centre on sheer force. By contrast, Dante has numerous tricks that could make Shunsui's tricks almost useless, namely Doppelganger making both Kageoni and Takaoni useless by both removing his shadow and allowing him to be in two places at once. Nero does not have this or anything like it, nor does he have the experience required. His phantom is Vergil, so it may have some knowledge to give him, and would help his skill somewhat, but Vergil was never greatly adaptive either.
In short, Nero has the advantage in strength and can take more damage, but Shunsui is faster and his various tricks combined with his greater speed and skill would allow him to keep one step ahead of Nero for the entire fight.