Watanuki Kimihiro and Doumeki Shizuka

This is the relationship that during the series changes the most from the first meeting till to what is happening in the last chapters of the series.
Watanuki has problems accepting Doumeki, he often reacts to words with anger, the bespectacled boy decided on no evidence that Himawari had some interest in Doumeki and vice versa. But that doesn’t stop for the bond to grow… Watanuki is the one who draws the evil spirits to himself, while Doumeki is the one who dispels them, so in his own best interest, Watanuki has to keep Doumeki near himself.

One who sees and draws spirits to him. And one who can exorcise them.
- XXXHOLiC, Vol 2, p. 175

Another interesting thing is that this relationship was voted the most in the readers pool for the Offical XXXHOLiC guide, and won with 554 votes, behind with only 207 votes is the one between Yuuko and Watanuki. This relationship is mostly enjoyed because of the contrast between the two characters.

There is a great combination between the emotional Watanuki and calm, relaxed Doumeki.
- Offical XXXHOLiC Gude, p. 140

It almost seems that the relationship is based on the fact that Doumeki saves Watanuki almost every time they have a mission or when they are together, which makes their bond even deeper. And that causes the two to pass more time together, because Watanuki feels in dept with the other boy, and because of that makes him bento, along with constant complaints and insults. The fact is that every time something threatens Watanuki, Doumeki is there and pulls the shorter one:
1. in Volume 3 for example to save Watanuki from falling down and get killed, he injures his right arm
2. in Volume 4 he is the victim of Zashiki Warashi who wants to give chocolate to Watanuki on Valentine’s day and almost kills Doumeki at taking it directly from his stomach.
3. in Volume 5 Doumeki stands 10 hours under rain holding a ribbon because Watanuki vanished under hydrangeas.
4. in Volume 6 Doumeki puts their friendship on line, to save Watanuki’s life, and there is actually shown how much the boy cares for the bespectacled boy, so much that he is prepared to renounce his friendship if that means saving Watanuki’s life.

He made a decision. He chose to shoot the woman. Even if it hurt you, even if it made you hate him, he didn’t want you to vanish forever.
- XXXHOLiC, Vol 6, pp. 152-153

I shall continue this part when I see where CLAMP are leading us with the series, for now… I’ll stop here.