@Loonila205 exactly. Before Miyo he literally kicked out countless ladies, they can't force him into accept this attention whore.
The other dude just wants Mio and her priceless bloodline, he couldn't care less about what happens to Kaya after; she'll likely face the bulk of the blame for the incident now that everything is blowing in their faces and since is well-known how their father favored the mistress daughter is a perfect scapegoat.
Kouji is indeed just weak but to decide for another life that the end is the only option is extremely arrogant and self-centered and if he doesn't die he'll pay the price.