What is the relationship between Clow Reed and Ichihara Yuko?

Question

According here,

Clow had accidentally wished for Yuko to live, thus severing her time from all dimensions. Clow regretted this wish, and no longer wanted the title of "world's most powerful magician".

Though it was said on the same link that their relationship is unclear and that Clow Reed had a former lover named Madoushi (appeared in Cardcaptor Sakura Movie 1), I would still like to ask (because someone here might know) how Clow Reed and Yuko is related. Clow Reed wouldn't have wished for Yuko to still live if there was nothing deep in their relationship. So are there any formal statements from CLAMP about their real relationship and the story behind Clow Reed wishing for Yuko to live?

Answer 1

For one thing, it wasn't a very deep thought that caused him to wish for her to still be alive. Instead, according to here:

Upon her death, Yuuko finally explains her connections with Clow Reed. As Yuuko lay dying, Clow Reed had the briefest thought that he wanted her to remain alive. Clow's magic was so powerful that this single thought caused Yuuko to become frozen in time.

Additionally, according to here:

In Tsubasa: RESERVoir CHRoNiCLE, Clow Reed is mentioned by Yuko frequently. They seem to have worked together for the same event that Yuko always talks about: "the day that has to come". For this purpose, both created the Mokonas (which implies that they had met the "Real" Mokona of Cephiro).

As far as I can tell from everything I've read, they are not related by blood. Instead, they worked together. They may have been no more than acquaintances or maybe friends, as there seem to be few implications that they were ever anything more.

The only time I have seen it implied was in Chapter 138 of Tsubasa, where Clow said to Sakura, "Being apart from the one you like, no matter how old you are, is a lonely thing. And while apart, I'm wishing for that person to be happy." There are thoughts that he may have been talking about Yuuko. It is possible that he was talking about Madoushi, but Madoushi only appeared in an anime movie and so may not have been canon to the manga.

I cannot find any official statements on the matter, though.

Answer 2

It's not directly stated, but this being Clamp, whose themes often revolve around love, it seems highly likely that Yūko and Clow Reed were in some kind of a romantic relationship. That's the impression I got from reading Tsubasa and xxxHolic.

The evidence:

1. Yūko is always badmouthing Clow Reed. However, there isn't any real hostility in her words. This implies a high level of familiarity with him.
2. Clow Reed wished to save Yūko. It's stated in the other answer that it was only a single passing thought that brought his wish into reality, due to his powerful magic. But such a mistake really isn't what Clow Reed is known for. My guess is he cared about Yuko a whole lot to slip up like that. Additionally, this situation parallels the one between Syaoran and Sakura, where Syaoran ends up making a wish that stops Sakura's time, so that she won't die. I highly doubt this similarity is a coincidence. And Sakura and Syaoran are confirmed to love each other.
3. Watanuki is stated to resemble Clow Reed. And...

By the end of xxxHolic, Yūko is gone, and Watanuki decides he will wait for her in the shop, no matter how long it takes, and no matter how unlikely it is he'll see her again. It is clear he feels some kind of love for Yūko (not necessarily romantic, but I'm not discounting it either). He goes so far to choose this love at the expense of all of his other relationships.

I got the impression that Yūko and Clow Reed were in a romantic relationship, but this isn't solely me making stuff up, as other fans noticed long before. Clow Reed's page here notes

Clow and Yūko had a past relationship. It is theorized that he and Yūko were lovers. He and Yūko made the two Mokonas together.

As far as Madoushi goes, when I watched that movie, I got the impression her love was unrequited. Her Wiki page even states,

She started developing feelings for him, but it isn't indicated if [Clow Reed] returned the feelings. She constantly made mention that there was something she wanted to tell him, presumably that she loved him.