After Mishima Geki Nyudo followed Muromachi period kanrei (Shogun's deputy) Yoriyuki HOSOKAWA into death, the custom of committing seppuku during peacetime following the death of one's master due to natural causes began.
室町時代の管領細川頼之に殉死した三島外記入道以来、平時に病死した主君に対して行う殉死の風習が始まった。