Replying...
Intro. Nayuri is a Woman in One Piece, she is Law's almost sister and Luffy's best friend... everyone knows that.... but no one knows his past, only Law knows... NAYURI'S SAD PAST As a little girl she always smiled, she was confident of herself and loved to play. Then when she turned 10 years old she realized the reality of the world, her older brother (Biologically) named Neyutso had died, her old personality had been destroyed and now they saw her smile, but that was not her true smile, and when she lies down on the grass (reference to Why are you leaving?) she feels that her deceased brother is next to her. She also takes some happiness pills, those pills make her happy as long as she doesn't take them, she suffers remembering her past, (she does that in her room). She is also half-demon and her demonic transformations are also affected by Nayuri's past traumas

Nayuri and her sad past - One piece

@Neyutso