I liked the action and ideas. You established the three tutors fairly well (though memorable physical/verbal traits would be useful). I enjoyed the contrast between the father’s ideals and the mother’s quiet influence. The dad drawn into a duel – very cool.
You switch from present to past fairly frequently. Also, some weird grammar, like “I’ll fight with you if I weren’t joining General Ishi’s campaign.”
Remove words and clauses to make sentences punchier. Edit down, use concrete descriptions and details. Show, don’t tell. Travel and bathroom breaks can be summarized, but use details, action, or dialog to vividly imply an afternoon’s activity. Don’t use passive voice or “to be” verbs unless unavoidable, or for effect (e.g. “The man’s face is unflinching as his bowels are spilled upon the courtyard cobbles.”)
Give the intro a hook. A clumsy description of scenery and the fact that night follows day doesn’t exactly grab the reader. Perhaps Taru is looking at something on the sly during his lessons, or whatever. Emphasize his boyish nature barely constrained by the mores and traditions of ancient Japanese society.
Don’t use “naginata” when “spear” works just as well. Don’t make me look up “ashigaru” when I’ll immediately understand “foot-soldiers.” These add confusion, not flavor. If you must, say “your father’s long katana sword,” or “naginata spears.” Foreign names are already hard for readers, keep the number of foreign words they must learn to a minimum. Name suffixes are also asking for trouble. Instead of a suffix lesson interrupting your story, I would just say “Mistress Tomoe” or leave them off completely.
The kanji for Taru don’t show up on my Mac with Japanese fonts installed.
You mention Jiru being born, then the next page is “Yet, for all the fortunes he has forged upon the deaths he had caused, he is not exempted from a meeting with Enma-O.” It’s not clear it’s your father. Also, Enma-o needs explained.
That Yoshimaru killed a peasant’s son unjustly and your father challenges him to a duel is clear, but your father said “now” and then without explaining he gets permission and then starts on a trip to the city. Also, Taru seems unaffected by it all, when I would hope he would be extremely tense, lose his appetite, etc. In general, Taru is too disconnected, not portrayed as a boy. The events are supposedly through his/our eyes, yet not narrated in a way a real person would experience them. Viewpoint also confusingly switches to omniscient (and irrelevant) facts.
Given how idealistic the father is, would he really kill the bandits right in front of his son? Or just turn them over to the guards?