Although Kongou trusts him, Hamakaze doesn't really believe in him because, well, he's kind of an unprofessional slob. I find that kind of funny because these girls are a prime example of not "judging a book by its cover". I get why she's so hesitant though.
...II'd like to try believing in him—in Setogawa-san.What do you want to do, Hamakaze?I need more proof.That it's all right—For us to follow this person without any hesitation...I will find Setogawa-san.*turn*Please have tea with the others.