Mystery Disc Series

The Mystery Disc Series is the twenty-first series of the Treasure Hoard in the Japanese version of. It is comprised of fourteen covers of various brands of milk that are popular in Japan. It is the only series exclusive to the Japanese version, possibly because none of the brands are known internationally.

Ship's announcement
謎の円盤群シリーズがそろいました！ どれも似ていますが、セールストークで異質感を演出してみせます！

English translation: You've collected the Mystery Disc Series! All these objects may look similar, but I gave them different sales pitches based on their textures!