Ordinary people simply did not possess the means to detect enemies entirely through Observation Haki. Under normal circumstances, how far could their detection range possibly extend?
By the time they had the leisure to do that, their eyes would have probably seen it already.
So this move was only useful against enemies with an enormous Observation Haki range.
Because although that patch of "darkness" drew attention, the other side could not see through that "darkness" to predict the movements of the enemies inside.
Just like now, Ron had only noticed Yasopp's bullet after it left the barrel. The two had worked together flawlessly, allowing Beckman to avoid certain death while dealing Ron a devastating blow.
"Thanks, Yasopp!"
Beckman gave a thumbs-up and grinned.
"Heh! We have to let this arrogant brat know that we're not useless trash!"
Yasopp rested his smoking sniper rifle back on its stand and rubbed his nose.
"Admiral!"
Onigumo and the others watched with fury burning in their eyes and were just about to charge forward when they suddenly saw Ron raise a hand and clench it tightly.
Crack!
Yasopp instantly turned around in terror. He watched the inhuman Lightning Clone bend toward him, its mouth stretching into an impossibly wide arc as it revealed an evil grin.
Boom...!!!
Then, the blue crayon-sketched figure violently exploded atop the Red Force, blasting the ship into a sharp outward tilt.
"Yasopp!!"
Beckman roared in shock and rage. Then he suddenly realized something and whipped around. "You... did that on purpose!"
"Or else?"
Ron calmly lowered his hand and raised the Thunder Dragon Halberd. "You all know me so well. How could I possibly not know you?"
Through the constantly healing muscles of Ron's chest, Beckman could clearly see the Seastone bullet he had fired lodged in the deck.