One Piece (1999)

S1E34 Everyone's Gathered! Usopp Speaks the Truth About Nami!

Johnny reveals to the crew that Nami has killed Usopp, but Luffy is skeptical until Nami shows up and admits it herself. She warns them to mind their own affairs and leave her behind, but Luffy, determined, chooses to remain on the island. Moments later, Usopp reappears, clarifying that Nami only faked his death. Nami's sister, Nojiko, then begins to shed light on the reasons behind Nami's unusual behavior.