With that said however, the focus of the story actually shifts quite a bit as the plot unfolds. I believe that taken broadly, the plot development can be split into two between the main characters of the story. And yes, I know some of you would like to keep believing that Maria was as much of a co-main heroine as Nagi, but that just wasn't the case in actual practice, so let's leave it at that.
The First Half
For the first hundred chapters or so of the story, the focal character is actually Hayate himself. We are made to empathize with his plight and how he is always getting himself into trouble -- especially given how much of a brat his mistress is.
We also get to see a darker, more jaded side of Hayate as the story goes on -- especially in how he deals with characters like Yukiji, Kotetsu, and even the student council trio.
This continues on for a while until we reach the highly touted End of the World and Golden Week arcs of the manga, wherein his tragic love story with Athena is introduced. It is at this point wherein the spotlight is slowly being shifted towards Hayate's co-main character, Nagi Sanzen'in.
While the entirety of the Golden Week arc is still arguably Hayate's story and how he comes to terms with his past, it is also the part where Nagi's character shines the most at that point in the manga. It is probably the first time wherein Nagi does something awesome and of her own volition -- AND without being a brat about it. Unlike previous chapters, Hata does not take away from Nagi's moment of awesome by ending it with a gag. This is because we are being prepared for the second half of the plot -- Nagi's side.
The Second Half
In the first volume of the manga, Nagi says that the story starts to get interesting when the girl starts taking charge -- well, that's exactly what she does at the second half of the story -- and really, she never lets go of the spotlight.
The comisun arc, or Nagi's epic mangaka battle with Ruka is really the point wherein the focus of the story has permanently shifted to Nagi. Naturally, Hayate still plays a big role and is actually shown on-panel more often than Nagi -- but something has changed at this point: the focus character of the story is now on Nagi. Even the epic King's Jewels plotline has now been waylaid in favor of Nagi and her mangaka antics -- and this is what threw a lot of people off.
People who were still riding high on the Athena x Hayate failed love story from the previous arc expected more harem hijinks and more focus on Hayate and his ongoing quest for love -- which just didn't happen. In fact, even when Nagi is not on-panel, it is often painfully obvious that she has hijacked the story -- it's all about her now and people who were expecting something else would just end up sorely disappointed.
However, for people who were waiting for Nagi's chance to shine, the mangaka arc was really a godsend. Nagi is really put through the wringer in this arc and really, for someone as spoiled as she was, going through such traumatic failures and realizations during this arc must have been a hellish nightmare. It would probably be enough to break any normal person -- but of course, while breaking down several times, Nagi somehow manages to pick herself back up and becomes the amazing girl that we see when we reach the finale.
Unfortunately, a lot of people were still stuck on the idea that Nagi is just "one of the main heroines," while completely ignoring the fact that her story arc in fact now dominated the entire plot from the moment the mangaka arc kicked in. It was plainly obvious that the King's Jewel backstory was just being slowly developed in the background, but even when it did come back into the foreground, it was now an integral part of Nagi's own story.
As for Hayate, while his character development was still being subtly worked on, it never gained the same prominence that it had during the first half of the story. This is plainly obvious when even his own feelings for Nagi weren't really fully addressed because of the two year timeskip. While there is a lot that Hata has said about how Hayate chose Nagi in his blog and in the supplemental materials, when the manga is taken as is, it is pretty hard to understand what Hayate was really thinking after the Golden Week arc.
However, Nagi becoming the focal character after that arc and eventually being the girl that Hayate chooses to love was actually foreshadowed in chapter 252 when the narrator says, "with those words, he had seen the future." Referring to Nagi's words to Hayate at that time. In fact, there is a whole slew of foreshadowing sequences for a Hayate x Nagi ending in the Golden Week arc alone -- without counting the various other clues that Hata left throughout the entire story.
Over-all, it can be said that Hayate's personal character development faded into the background in favor of his eventual romantic partner by the time that the mangaka arc kicked in.
That's all I have to say on the matter for this week. I leave you with a Hayanagi fanart.
Title: Their Special Place
Medium: Oil Pastels on Canvas
Title: Beyond The Starry Skies
Medium: Oil Pastels on Paper