Monster Hunter: Open Ocean. (One Piece x Monster Hunter)

Trials of Iron and Swamp! A Deadly Survival Game!!

With Luffy...

A loud bang rang out across the jungle as the raider fired his bazooka, intending to kill the Straw Hat boy once and for all.  When the smoke cleared, however, he was annoyed to see the boy alive and well, having inflated his body to absorb the impact and deflect the shot. 

"This is the eighth time already!  Give it up!", Luffy shouted, annoyed that the raider was wasting his time.  The raider smirked down at him.

"In that case, time to change my strategy", the raider decided.  He opened a compartment near the top of his bazooka, and slipped a dial shell into it before closing it with a click.  Aiming his bazooka at Luffy, a powerful gust was emitted from the weapon, the smell of which made Luffy's face crinkle in disgust.

"Ah!  Gross!  What's that smell!?", Luffy shouted, the foul, sulfuric odor assaulting his sensitive nostrils.  

"There was natural gas in that breath dial", the raider said, "This weapon is called a burn bazooka.  It creates flames using the gas emitted from the breath dial, and disintegrates my victims!"

The raider pulled the trigger on the bazooka, unleashing a gigantic blast of fire from the barrel.  Luffy barely avoided the blast, the intense heat burning all plants in its path, including a massive tree that had a giant hole burned through its trunk.  The terrified screams of numerous animals rang out through the forest, with some of them no doubt getting caught in the flames' path.  Luffy screamed as he sailed through the air, landing flat on his butt.  

"WHAT THE HECK WAS THAT!?", he shrieked, rubbing his sore behind, "IT BURNED RIGHT THROUGH THAT HUGE TREE!"

Remembering his enemy, he leapt up and whipped his head around, scanning the trees for his elusive foe.  

"Where did that guy go?", he grumbled, before a sudden shift in the air caught his attention.  He turned around, and just narrowly leaned back enough to avoid a kick from  the masked man.  As he leaned back, he placed a hand firmly on the ground to balance himself.  

"Gomu Gomu no Pistol!", he roared, launching himself up and swinging a punch.  The masked man brought a foot up to block the strike, then pushed off with a hard shove, raising his bazooka for a counterattack.

The shot from his bazooka narrowly missed as Luffy forced himself to his feet, evading the blast and sprinting towards his opponent.  The masked man gritted his teeth in frustration as the boy refused to go down.  His eyes narrowed as he watched the boy swing his leg back for a kick, before widening as he whipped his leg forward with blinding speed.  

The kick struck with enough force to kick up a dust cloud, leaving Luffy unable to see his target.  When the dust finally settled, he was shocked and annoyed to see the man had blocked his kick with another.  It was not a perfect block, however, and the warrior was obviously struggling against Luffy's raw physical strength.  This was evident by his gritted teeth and heaving breaths.  Luffy audibly growled in frustration, and began wildly kicking at his opponent, furiously trying to land a hit.  The guerrilla blocked every strike, and retaliated with another blast from his bazooka.  Luffy dodged backwards, and the man leapt into the trees.  Luffy then wrapped his left arm around a tree branch, launching himself up for his next attack.

"I won't lose in a bazooka competition!", Luffy declared, arms stretching far behind him.  The guerrilla responded in kind by raising his weapon for another attack, eyes narrowed at the young pirate with burning hatred and ferocity.  Luffy's arms shot forward at breakneck speed, meeting the bazooka's burning blast head on before piercing right through.  The guerrilla's eyes widened for a brief moment before he was struck dead center, head falling back as he coughed up blood.  The force from the strike threw him back, momentarily winding him.  Slowly, the wounded fighter forced himself to sit up, hands resting upon his thighs as ragged breaths past his lips.  When the smoke from the blast cleared, a bloodied Luffy glared at the wounded guerrilla, blood dripping from his mouth.  Both warriors were evenly matched in speed and raw determination, with neither able to surpass the other with strength alone.