From MangaHelpers:

The year is 1563 and the people of the Minonokuni were faced with the choice of siding with the Saito family or the Oda family. As a vassal of the Saito family, the Sengoku family makes the decision to betray the Saito family and join the Oda family. As a member of the Sengoku and in a close relationship with the Saito, Hisakatsu was forced to be disowned by the Sengoku family to protect his younger brother, Sonjiro. With his extraordinary skills in swordsmanship, Hisakatsu fights his way out of Minonokuni in order to protect his brother. [DrCoke]