Conversation so far:
What were some of Miyamoto Musashi's teachings?
Miyamoto Musashi created and refined a two-sword kenjutsu technique called niten'ichi or nitōichi or 'Niten Ichi-ryū'.
Did Miyamoto Musashi write any books?
Musashi's most famous book is the The Book of the Five Rings.
What was The Book of the Five Rings by Miyamoto Musashi about?
Musashi seems to take a very philosophical approach to looking at the craft of war in The Book of Five Rings.
What else was Miyamoto Musashi known for with his teachings besides his books and style of sword fighting?
Miyamoto Musashi spent many years studying Buddhism and swordsmanship. He was an accomplished artist, sculptor, and calligrapher. Records also show that he had architectural skills.
Did Miyamoto Musashi have any famous paintings or sculptures?
Miyamoto Musashi especially mastered the broken ink school of landscapes, applying it to other subjects, such as his Kobokumeikakuzu Shrike Perched on a Withered Branch.

Question: What language is his writings originally in?
Self-contained rewrite: What language is Miyamoto Musashi's writings originally in?