Shui Wai-ming (水慧明), better known as Queen, is a Scientific Evidence Officer (SEO) from the Forensic Science Division of the Hong Kong General Laboratory.
In episode 16, she found out that her boyfriend, Louis, and her best friend, Elaine, had a one night stand so she broke up with him.
Thanks to King Sir's support and encouragement, she was able to bestir herself, and they became close friends and each other's ‘tree hole’.
However, even though she knew King Sir has feelings for her, she did not accept his confession for fear of losing him, like how she once lost her father.
Charm Ting (湛霆) is a Scientific Evidence Officer (SEO) from the Forensic Science Division of the Hong Kong General Laboratory.
Dr. Man followed her sister's dream to be a forensic pathologist and gradually developed passion for her career.
In episode 9, Dr. Man met her deceased sister's boyfriend, Stan, again and they become close friends.
Senior Inspector (SIP) Kwok Fai-wong (郭輝煌), better known as King Sir, is the head of the Kowloon West Regional Crime Unit with high case closure rate.
When King Sir was young, he watched waves with his brother-in-law at the seaside during a typhoon and accidentally fell into the sea.
King Sir is Ko On and Dr. Man's good friend, and cooperates with them to crack cases with their professional teams.
She has a close relationship with her elder brother, Ko On, and respects her supervisor, King Sir.
Chris Tsui Yi (徐意) is an online news reporter, who occasionally provides clues for case investigations.
She then lived with her uncle and aunt from her mother's side, who forced her to take part in child abduction.
In episode 25, her friend Paul managed to trace Ko Sin's whereabouts to an orphanage in San Francisco.
Stan Sze Kin-yin (施見賢) is a voiceprint expert who occasionally assists in case investigations with his expertise.