Well, the best chances of Itsuki winning are that, as a heroine, she most closely embodies the theme of the manga. Being (5) and her development somewhat parallels F's own. Not to mention, as a heroine, she's had the biggest impact and challenged Negi's views the most, which to me matters far more than confessing or whatever.
That said, her character arc isn't at all reliant on romance, and we could easily see her become a platonic, mentor kind of character. >>180213638
If he makes it a rejection on the spot, that removes the dramatic tension. The issue isn't the delay or whatever, it's the development of plot structures. Let's use the Japanese model, ???? - Ki Sho Ten Ketsu, or introduction, development, twist, and conclusion. >Ki - Nino meets, confronts Fuutarou, immediately hates him>Sho - Nino and Fuutarou grow closer, learn about one another>Ten - Nino realizes she's in love and confesses to F>Ketsu - Nino confesses again, drives the point home
Now, let's look at how these two scenarios would fit into this structure. If Nino accepts, that forms part of the Ketsu. Everything is dandy, Nino gets her reward for growing as a person. ?????????? all around. There's little reason not to show it there. Everything gets wrapped up.
If, however, the response is rejection or ambiguous, that leaves room for more conflict, more dilemmas, more misunderstandings and confusion. That's not part of the Ketsu, that's more like a second Sho or Ten. Which tends to fuck up story pacing.
So what authors sometimes do is exactly this, skip to a different story, let that brew, and then flashback to the rejection someplace down the line, when the atmosphere is more appropriate for that kind of twist. Again, I'm not anti-Nino, I just think that's what the writer is trying to do here.