Jubei, his legitimate son, became blind in one eye because Munenori struck him by mistake during a sword-sparring session to instruct a fencing technique called Tsukikage no tachi (Moonshadow sword).
嫡子・十兵衛が隻眼になったのは、宗矩が月影の太刀伝授中に誤って傷つけたためと言われている。