Nagisa Amami is a 26-year-old office worker who stands 153 centimeters tall and was born on August 31. She is the protagonist of the story and begins as a shy, insecure woman who has never had a romantic relationship. This lack of love experience weighs on her self-esteem, driving her to take a trip with the goal of changing herself and becoming more confident. During this journey, she has a chance encounter with a yakuza member named Soushi Sazanami, who asks her to pretend to be his wife for one night. This meeting sets the course of her story.

Her primary motivation is a desire for personal growth and to overcome her shyness. She is initially naive and sheltered, but she shows a willingness to step outside her comfort zone. As she becomes involved with Sazanami, her role in the narrative shifts from that of a lonely office worker to a woman navigating a dangerous and unfamiliar world of organized crime. Her relationship with Sazanami is central: he is a smart and gentlemanly yakuza who treats her with unexpected care, which both surprises and unsettles her. She also has a childhood friend named Daichi Hinata, a police officer, who represents a contrasting, safer connection to her past.

Over the course of the story, Nagisa undergoes significant development. She learns to trust her own strength and intelligence, becoming more assertive and resilient as she faces the challenges of her new circumstances. While she starts out insecure, she gradually discovers an inner courage she did not know she had. She does not possess any special supernatural or combat abilities; her notable traits are her growing emotional fortitude, her capacity to adapt to difficult situations, and her determination to protect the people she cares about. Her journey is one of self-discovery and empowerment within the context of a dramatic, romantic relationship with a gangster.