Natsuki Sakai is a supporting character and the primary antagonist of Detective Conan: Magician of the Silver Sky. She works as a stylist and makeup artist for the famous actress Juri Maki. Her background is that of a skilled professional who secretly resents being treated like a servant by her employer. Her motivation is rooted in a missed opportunity: she was offered a prestigious position as a top makeup artist in Hollywood, but Juri refused to release her from her contract. This resentment drives her to murder.

In the story, she first appears backstage at the theatre where Juri is performing, preventing Ayumi Yoshida from touching Juri's makeup, which has already been laced with poison. Her role in the plot is that of the murderer: she poisons Juri's face powder with cyanide, knowing that Juri will touch her nose to equalize ear pressure during the flight and later lick her fingers while eating chocolate. Juri dies from cyanide poisoning mid-flight, and the ensuing crisis forces the plane into an emergency landing. Natsuki is eventually exposed as the culprit by Conan Edogawa and Eri Kisagi. After being apprehended, she expresses regret for her actions and is comforted by Professor Agasa, who tells her she can start anew after her imprisonment.

Her key relationship is with Juri Maki, whom she killed, but she also interacts briefly with the main cast as a suspect. She has no notable physical abilities; her expertise lies in makeup artistry, which she uses both for her profession and to commit the crime. Her development is limited to the film's narrative arc, where she moves from a seemingly loyal employee to a remorseful criminal.