Truthfully, beyond "an archer," there were no other ways that Watanuki could describe Doumeki (save for the multiplicative and inventive adjectives that he found he used out of sheer habit.) Not for wont of trying, but he simply... didn't know all that much about "the archer." Watanuki could count the number of things he knew about Doumeki on one hand.
Doumeki lived at a temple. Haruka, his grandfather, had been a priest. It was possible that Doumeki would become a priest, especially since he'd been thrust pretty forcefully into the occult by Watanuki's-wonderful-life-of-Hauntings (and yes, Hauntings did warrant its own Capitalization.) Watanuki felt slightly guilty on this part, but not so much because it was Doumeki's choice. "The archer" could simply have moved on with his life after the story ritual. Admittedly it would probably have been hard, but Doumeki had proven his own obstinacy more than a fair few times.
His birthday was on Hinamatsuri, he had been forced to dress as a girl as a child. He always ate everything Watanuki served to him, but he was a picky eater. He was good at sports, and had a particularly mean streak when he thought Watanuki was being stupid. He liked to drink, he had incredible luck. But even when Watanuki was being stupid, Doumeki would steadfastly protect him.
Okay, so maybe Watanuki knew more about Doumeki than the average person. But these were all things that Watanuki had observed or been told by Haruka. Never by Doumeki himself.
Doumeki was a superior archer. Obviously. The fact that Watanuki was still alive was a testament to this fact. Watanuki knew all of Doumeki's favorite foods, but those were... not important. Well they were important, but not in the way that he thought was Important. Like things he should remember. Things that brought empty pangs of misery when he thought about the things he should remember about two other people.
What if everything Watanuki knew about Doumeki was not everything he knew? What if he had forgotten something about Doumeki? What if he simply couldn't remember and that was the reason Doumeki stayed around? Watanuki could hardly remember things about himself! Nobody could be so frustrated about Watanuki's memory loss as himself. Nobody! But... there were some things that he would remember. Because Watanuki could be just as stubborn as Doumeki.
Because there were some things that are just that important.
And Watanuki realizes that Doumeki isn't as unfeeling as he used to think.
