Episode 8 of Trigun Stampede , " Our Home ," reveals crucial backstory about Vash and Nai immediately following the Big Fall, where Knives forces the SEEDS fleet to crash. After being found by survivors from Ship Three, Vash finds a new home and purpose, using his abilities to heal plants and taking on his signature red coat. The episode concludes with Vash discovering his brother's actions and deciding to leave Ship Three, vowing to confront him directly.
You can watch this episode and see the backstory unfold on Crunchyroll . Trigun Stampede 08 (Backstory #Trigun) [Anime Kage] Trigun Stampede - 08 [1080p RoSub]...