Trigun Stampede Episode 9 -

The episode primarily focuses on the backstory of Millions Knives, revealing the moment he truly broke from humanity.

: Knives discovers that humans are overworking Plants to their breaking point, causing them to turn red and eventually die. Trigun Stampede Episode 9

The episode also clarifies the origins of Vash’s iconic cybernetic arm. The episode primarily focuses on the backstory of