Masuda was a second cousin of Yukichi FUKUZAWA, and they lived close to each other and had a close relationship; however, in 1870 when Fukuzawa returned home, Masuda attempted to assassinate Fukuzawa being asleep.
福澤諭吉の再従弟に当たり、住まいも近所で親しい交際があったが、明治3年（1870年）、福澤が帰郷した際、寝込みを襲おうと暗殺を企てた。