Lol she basically already accepted him as her son-in-law.
Calling it now: the father is either going to be adamant that she marry the hero or he's going to be an overprotective, doting father who will vehemently oppose Youki getting close to her before inevitably liking him too.
I'm uncomfortable with the difference in closeness between Kotoko and Seo vs Amane and Seo. Someone might get the delusion that OUR Kotoko is gonna lose in the end. Of course, she wouldn't but as things stand I'm a bit concerned... for Seo. I'd hate to have to kill him, after all.