@Anteup321 Oooooooooh. I get it now. The dad wants to unite the families (probably to make Nagi his heir) and there's two ways to do it. Nagi marries Erika, OR Sachi marries Nagi2.
what are the chances that scholarly love interest girl (don't remember her name) turns out to be blood related, so she's out of the question? or she's also a "sister" and she's engaged to him already without either knowing it?
Man. That guy is a real asshole. He might genuinely believe that he's just "doing what's best," but he's really just manipulating all of them for his own shitty whims. Honestly, I just want Nagi to punch him in the mouth.