In her teenage years, Kiriko was the leader of an all-girls gang in Tokonosu. Later she joined the police and was a member of the mobile traffic unit. Being incredibly effective at keeping the peace, Kiriko was feared by all delinquents in the area. So much so that they dubbed her Precint Kiriko. Eventually she left the force when she met her to-be husband Tadashi. They married and later had their child, Rei. She has known Takashi Komuro since he was young.
While Kiriko Miyamoto was living with neighbors, close to her own home, to survive the outbreak, things were going well. She got along with everyone until they had let in some new stranger. After they sent her out to gather food alone, she returned and they refused to let her back in. As she was banging on the gate, Her own daughter, Rei, called out to her. After the joyful reunion, she told Rei and her friends about how she wound up in this situation. Takashi invites Kiriko to join their group as they move to the Shintoko Third Elementary School, where the J.S.D.F.(Japanese Self Defense Force) have been organizing the evacuations. She tried to tell the people inside about the evacuation, but they refused to believe her.
Having given up on the neighbors, Kiriko was now with Team Takashi. When Rei asked about her father, she could only tell her that she hadn't heard from him but was sure he was still alive. She had a spear as a weapon, but Kohta also gave her an automatic pistol he got at the police station. Now armed, the group moves along quietly so as not to draw the attention of Them that had been approaching before.
Kiriko's main weapon is a spear that is used in traditional spear martial arts and belongs to her husband. After she joined Team Takashi, Kohta Hirano gave her an automatic pistol that he acquired from the police station they had been at earlier.