Shioya Reiko and Sato Naomi are ordinary women in their 60s. Reiko is the head of an elementary school while Naomi is a grandmother with a sharp tongue, but cannot stand up to her grandson, Yuta. Naomi is delighted to have her daughter, Tomomi, and family come to live together with her. Tomomi and her husband, Masuo, decided to change schools and relocate after Yuta refused to attend school because he was being bullied. Yuta quickly makes friends with Chika who lives next door. The next day, Naomi takes him to elementary school on behalf of her daughter. She meets Reiko, who heads the school and is an old friend, at the opening address. In fact, the two of them were once special investigators with the code names “Salt & Sugar” and they were responsible for covert Japan-US diplomatic espionage. Their last assignment was more than 20 years ago. Naomi, who is suspicious of her neighbour, Takanashi Yoichiro, establishes contact with their former boss, Tokita. Knowing that Chika is Yoichiro’s daughter, she tries to find a solution that will not hurt Yuta. However, Tokita and his subordinate, Shichimi, stop at nothing to force her to proceed with the mission. She and Reiko team up again to uncover the true identity of Yoichiro in an attempt to stop a crime.