So fuckin ridiculous. He was willing to give them all the benefit of the doubt no matter how many times they proved they weren't Ainu... but the moment they got Asirpa's character wrong, that triggers him.
I love Sugimoto in this chapter. His open mindedness being used against him as he just accepts their butchering of Ainu culture, and then the immediate 180 when they claim Asirpa was actually acting like a normal girl.