五輪書
In the second month of 1641, Musashi wrote a work called the "Hyoho Sanju Go" ("Thirty-five Instructions on Strategy") for Hosokawa Tadatoshi, this work overlapped and formed the basis for the later "The Book of Five Rings". This was the year that his adopted son, Hirao Yoemon, became Master of Arms for the Owari fief. In 1642, Musashi suffered attacks of neuralgia, foreshadowing his future ill-health. In 1643 he retired to a cave named "Reigandō" as a hermit to write "The Book of Five Rings". He finished it in the second month of 1645. On the twelfth of the fifth month, sensing his impending death, Musashi bequeathed his worldly possessions, after giving his manuscript copy of "The Book of Five Rings" to the younger brother of Terao Magonojo, his closest disciple. He died in Reigandō cave around June 13, 1645 ("Shōhō 2, 19th day of the 5th month"). The "Hyoho senshi denki" described his passing: