DCDX is a Christmas fandisc for the D.C. series. The highlight are crossover stories where the characters from both D.C. and D.C.II appear together (in a wide array of santa outfits).
In D.C. ~Christmas Mirai Koi Yume~, Junichi and his friends get caught in a sudden burst of light and end up 53 years in the future. Is this really what the future looks like? How will they return to their original time?
In D.C. II ~Day Dream Believer~, Yoshiyuki is preparing the ‘sexy sushi party’ at this year’s Christmas party at Kazami Gakuen. He’s called by Sakura, but when he gets to her office, he finds a small iron door that he had never noticed before. Curosity got the better of him and he went through door, ending up in the school’s hallway during Christmas party preparations… half a century ago! He went back and got his friends to check it out too, but soon there’s trouble.
[From Hau~ Omochikaeri!]