Hotarugusa

Nana is a servant of the Kazahaya family, She is from a samurai family. Her father was about to reveal wrongdoings within the domain but had to commit ritual suicide for a crime he hadn't done. Ichinoshin tries to correct the wrongdoings but ends up being a target himself. After finding out her father's enemy is the man behind it all, Nana decides to protect Ichinoshin and his children, as she had promised Sachi, Ichinoshin's late wife.
(Source: Dramawiki)
~~ Adapted from the novel by Hamuro Rin.