Killer B and Motoi

Battling his own shadow at the Falls of Truth, Naruto turns to Motoi to learn how Killer B mastered his dark side. Given how much peace hinges on Naruto controlling the Nine-Tails, Motoi agrees and, with Yamato listening, lays out B's history. His father Furui was killed when the Eight-Tails ran wild after its former host lost the reins, and B was picked as the replacement jinchuriki, then treated as an outcast. Blaming the beast for his father's death, Motoi turned that hatred onto B and twice came at him with a kunai. The first time B seemed to notice; the second, Motoi instead watched villagers hurl eggs at B, who only grinned and shrugged it off.

Naruto steps away to be alone, and the Giant Squid ambushes the others, snatching Motoi. Yamato locks it down with his Wood Release: Smothering Binding Technique. Naruto holds back, convinced the squid is B in his Eight-Tails form venting on Motoi, but the real B arrives and puts the creature away quickly. When Motoi asks why B would rescue a man who once meant to kill him, B answers that he remembers none of it, only the good years spent growing up with the person he calls his best friend. They trade a fist-bump, and Naruto picks up B's rapping speech tic while B mirrors him in turn.

Set during the Fourth Shinobi World War: Countdown arc, the episode adapts chapters 493 and 494. Its heart is the flashback that reframes B not as a monster to fear but as someone who chose warmth over grudges.