Time
Ryu's movements were swift and yet somehow unhurried. If there were individuals here to observe him, they would see a young man that looked as though he was taking leisurely steps, and yet crossing impossibly vast distances with every step.
Those that might have a chance to observe him, though, quickly found that there were ripped from them.
Ryu completely embodied the nature of his twin daggers, his body moving like the wind and his intentions being akin to lingering shadows. Flashes of lightning were all these individuals saw before their bodies fell into a rain of ash, unable to hold onto their lives.
Although Ryu moved quickly, he was actually being extremely cautious. There wasn't an inch that he stepped upon that didn't first withstand the scanning of his soul. However, he quickly found that many of the potential issues he ran into had been forcibly broken by others already.