Setsuke grew up around Ian Nottingham, and has loved him since she was a child. Nottingham's enemies foolishly believe that this makes her a hostage worth taking, that Ian might be emotionally vulnerable; they are utterly wrong in such beliefs.

Setsuke was kidnapped during the New York Museum of National History incident, 'though quickly rescued by Nottingham and Sara Pezzini. She has since tried to develop a relationship with Ian, 'though the assassin still considers her as a daughter, not a lover.

Since launching an attack against Gavin Taylor, Setsuke has become a thorn in Kenneth Irons' side, an intolerable liability. In a fitting display of irony, Irons has deemed that Nottingham should 'solve' the problem.