Osaka 1590. Aki, the youngest daughter of an Osaka cloth merchant, knows her father will marry her off one day. She isn't prepared for her callous and greedy uncle to announce plans to adopt her to arrange a marriage advantageous to him.

Samurai Nishioji Tomi works for the Osaka Police as a cover for finding a clandestine anti-Christian conspiracy group. His biggest challenges, though, are hiding his Christian faith, which is under suspicion, and his mother's illness, which could get her banished.

When Tomi arrests Aki's father for tax evasion, the samurai finds himself impressed by Aki's devotion in proving her father's innocence. He extends her a temporary position as his mother's caregiver, and Aki accepts to forestall her uncle's plans. But when efforts to find silk smugglers implicate Aki's family and an old enemy arises to seek Tomi's death, will the family secrets each holds be the weapons that destroy them?