What is the main conflict in Musashi by Eiji Yoshikawa?

Musashi—known at the beginning of the story as Takezo—and Matahachi, friends from the same village who had joined the military together, wake on the battlefield to realize that they are among the few survivors. Both are wounded and fear capture. When they find a small farmhouse, they ask for help and a woman named Oko allows them to sleep in the woodshed. Her daughter, Akemi, brings them medicine and food and they discover she is the girl at the battlefield and that she was robbing corpses on orders from her mother. Healed, the two decide to leave but Musashi wakes to find that Matahachi has left with Oko and Akemi. Matahachi lives off the two for some time as they run a tea house. His failure to return to his own village prompts his mother, Osugi, to hate Musashi and to vow that she will kill him. Musashi is briefly captured by the opposing army but Matahachi's former fiancée, Otsu, helps him escape. He soon parts with her, determined to follow the way of the sword.