I would have liked it better if he got to know that she was the girl from his childhood and interacted with her a bit more and then made the decision.
Otherwise it's like he chose her simply because she looks out for her sisters and sidelined herself. There had barely been any romantic...
Well the manga has been selling like hot cakes so the author probably wants to milk it as much as possible before concluding.
I am sure suddenly its popularity will drop and author would be forced to conclude in a few chapters making it end with a car-crash ending like Nisekoi.
Kazuya: OMG! Her knee is on my back! Her neck has small hair!
Readers: Shut up you simp! You have been going out with her for more than an year now. Give us the damn conclusion already, author!
Plot twist: She's been cursed to live forever only until they consummate their marriage. That's why she keeps postponing...
Apologies, just trying to bring logic to the events in this manga. I will see myself out now.