@OiGimmeMoreManga
1. "When in Rome, do as the Romans do" is not a comprehensive umbrella statement for taking in all of a culture's practices, including ones that grossly transgress the person in question's moral values.
2. That doesn't matter now, because A) he has only learned of this practice just then, and B) he will be forced to that practice in just a few days. Whether he should have learned about it earlier or not is just a 'what if' now that would no longer happen.
3. Again, the issue of genetics is currently moot, because neither of us can present concrete evidence of the presence or absence of deformities. Or do you actually have concrete evidence and/or sources?
4. Refusing outright does not mean definitely calling off the marriage, the father already stated it like a damn fact.
5. Except exactly because he has his former world's values that he won't take a practice that violates his moral values, especially if he wasn't even given time to take them in or adapt to the idea of the practice after knowing
6. No, he wasn't considering it. What the hell have you been reading? From the start, he had no intentions to marry her, and his love for her is only as an older brother. His excuses on the spot for his escape is the "well-being of the social life" of his sister, but that all happened in a time-limited period of crisis where his only goal is to escape this marriage. Later, he thinks of 'what ifs' but he still intends to push through with an escape.
7. Don't worry. While it is directed to you, it is also meant to answer lots of other comments. Just so happens that you are the most batsht crazy about this with at least 6 comments, maybe over 10 now?