From MangaHelpers:
In Edo Period Kyoto, Japan, the low-ranking samurai Amano Moritake serves the noble Hinonishi family. The Hinonishi family has become poor, but they still have a family treasure, an Awataguchi Hisakuni sword. Moritake is the guardian of this great treasure, and he protects the family from those who would want to take it from them. While in the service of the Hinonishi house, Moritake passes his days with the head of the family, Harusue, and his daughter Kaoruko. Together with the Hinonishi family, Moritake does his best to resolve each situation that comes their way.