Nagisa Natsunagi (夏凪 渚 Natsunagi Nagisa?) is the secondary main heroine and one of the main characters of The Detective is Already Dead. series. She is an 18-year-old high school student, who was the first client to request Kimihiko Kimizuka as a detective since after Siesta's death, to find someone.
Nagisa is an 18-year-old high school girl, considered to be beautiful by Kimihiko, with hip-length black hair that is tied in a short tail where it is pulled to the right side and it is tied by a red ribbon with bangs hanging over her forehead while she has ombre tips and red-brown eyes.
Nagisa has a strong personality, but she is a dominant character whose habit is to say "Die Twice".
As a child, Nagisa had a heart condition while she also had a weak and fragile body which forbid her from going outside and to school meaning she spent most of her childhood in a ward room's bed in an 'orphanage', later on revealed as a <SPES> experiment facility. One year before meeting Kimihiko Kimizuka, Nagisa received a heart transplant from an unknown donor that later was revealed Siesta was the donor. She inherited one of Siesta's "Seven Tools", the musket gun.
She inherited Hel 's red eyes ability, which allows her to control bodies at her own will.
- Nagisa means "beach, shore, water's edge" (渚?)
- Natsunagi means "summer" (夏?) (natsu) and "calm, lull" (凪?) (nagi).
- According to Nigozyu, Nagisa was intended to be the only main heroine in the manuscript submitted for the Rookie of the Year Award.