Yūko receives an invitation for the opening of an auction from a mysterious unknown sender. Likewise, fanatical collectors are summoned to an old mansion whose owner doesn't make an appearance. One after another, each collector disappears and a number of other strange occurrences happen during the night. The questions of what exactly it is that's being auctioned and who the owner of the mansion is must be solved in order for Yūko and Watanuki to get to the bottom of this.

[Source: Anime News Network]