Things, however, changed on February 27, 1613 when Shigemasa was punished by being deprived of his fiefs under an order of the bakufu (Japanese feudal government headed by a shogun) for violating a ban on private marriages on the ground that he had not registered marriage between his legitimate child, Shigenobu YAMAGUCHI, and Tadachika OKUBO's adopted daughter at the bakufu.
しかし慶長18年（1613年）1月8日、重政の嫡子・山口重信と大久保忠隣の養女との婚姻を幕府に届けなかったとして、私婚禁止違反であるとして幕命により改易された。