those were some dirty tricks by Ryohei, showing Otsu those visions. Being incredibly one-sided about it and placing all the blame solely on Musashi. hey, how about if he blamed himself and the Yoshioka for their incompetence, failing to kill one man and all. I'm glad that Otsu did not buy it at all.
I haven't read the book before but I believe that Vagabond is at the point where
Musashi will be offered a post by the Shogun, therefore, closing in to his duel with Kojiro.