Bankotsu merely continued drinking his sake. that spririt or whatever it was, didn't scare him, nor would his words sway him. Sicosan's intent and honor were for him to determine, not some sprit or puppet of naraku. If he brought him his swiord , reforged and on time, it would show that Sicosan was a man of his word,, If not... dprceror or not, he would deal with him like anyone else who had double crossed him..