Responses
well she'd be forced to marry someone likely not of her choosing (as her brother said, likely am old rich dude). He figures Arima would at least treat her well so she could be somewhat happy, even if it is a lie. So I don't think he's that mean
Mean older brother... I understand why but still, mean older brother, I tell you! Bringing someone else to misery land, completely on purpose... You're a mean older brother, Kuroki-kun.