How about using your fucking position as each factions' leaders to force them to stop the war? Fuck you Naoshi!
Nisekoi isn't exactly the most revolutionizing harem rom-com manga ever.
Yeah, this plot point makes no sense. I can only assume they're using the potential war as an excuse, and actually just want their kids to date and know they wouldn't be into it otherwise.
And they they forgot about the war or the yakuza boys doing yakuza things for over a hundred chapters.