Shortly after Matsubara became the leader of the Fourth Unit and instructor of jujutsu, he was strongly criticized by Toshizo HIJIKATA, the Vice Commander, for keeping a mistress (wife of a masterless samurai whom he had killed) near their quarters.
松原が四番隊組長並びに柔術師範となってからまもなく、松原は屯所の近くに愛人（自分が殺害した浪人の妻女）を囲っており、その件を副長の土方歳三に厳しく咎められた。