Note: Wrote on a prompt idea involving Hyuuga drawing someone important to his since back in school.
Often he found himself memorizing the smallest details. Etching then into papers as they came to mind, each detail as accurate as possible. If one were to tell him it was a perfect likeness he could easily state what was off. "No, the smirk is a little wider and not as high up" or "The hair usually moves this way a bit more." Some might find it odd he knew these things, but it was entirely normal to the sweet obsessed Major.
Often his drawings were of the one most important to him. Ayanami.
Now Hyuuga could admit perhaps his obsession with his long time friend was a bit much, but he could also admit he was unable to help it. He loved everything about the other and it became second nature to notice the smallest things about him. He memorized them and put them down on paper when he could.
Of course everyone started somewhere, he didn't excel in his work at first. Most don't. It took time to get as good as he was.
When he was younger he would occasionally doodle people around him, but no one stood out enough for him to focus on long enough to actually draw multiple times. He improved still, but had nothing to really compare them to as most people were easily forgotten soon after.
Until he met Ayanami.
When they crossed paths at first in the academy, something about that man struck him. He was everything Hyuuga considered perfect upon a first glance, someone he instantly found an air of interest to. Of course he took to following that person, having not really felt this before. He wasn't sure what it was at first, but over time he would learn that it was everything about this odd man that had caused him to become attached.
As the course of time continued and he spent more time with him, to a point one could say he devoted his life to this person. This person was someone he considered a friend and had found himself loving despite himself. He never questioned it, it was what is was. His precious Aya-tan was the most important person and as such, his doodles improved greatly in the mind set that "It must be as perfect as him."
His hobby and 'obsession' as some may call it led to him storing the drawings that weren't on important documents in a small haphazardly put together binder in his free time to prevent losing them.
As more hawks had joined them, he would doodle them as well, but none would ever be drawn more than the commander was. None of them would ever fill a binder worth like that man had. He spent so much time following him that he could draw him in any setting without having to reference him. Of course he still would watch wanting it to be perfect and simply because watching over his friend was something he was use to.
Some may call it an obsession, but he preferred devotion. Somehow he had fallen in love and devoted everything to that man. Even his hobby had become centered on him.
Was there really anything wrong with that? He didn't think so.