I am reading the manga Vagabond. After the death of Yoshioka Denshichirou, someone named Ueda Ryouhei is appointed as the head of the family. Ryouhei then makes a decision that the school should fight Musashi near Ichijou-ji Temple outside Kyoto.
But according to an answer on History Stack Exchange, it was the 12-year-old son of Seijuurou's, Yoshioka Matashichiro, doing this. Is Ueda Ryuhei a fictional character that has replaced Yoshioka Matashichiro? If so, why did the author not show Yoshioka Matashichiro in his comic?