Man, I honestly felt more sympathy for Hanayagi than I did pleasure for Katsuko. Her entire situation was her own doing for being too weak-willed to just give straight answers or be firm. And while what Hanayagi did was (self-admittedly by him) a bit underhanded, he wasn't doing it simply so he could mess around with a pretty woman but because he was genuinely in love. So having some shady guy blackmail and extort him into breaking things off with her is definitely worse and hell, it could even come back around on Shima if this isn't the end of it since he'd obviously think that Shima was behind all of it.