Board Thread:Questions and Answers/@comment-8028394-20130626122453/@comment-3582535-20130626124153

Apparently, one of the items you can find is the Bisque Doll (Tanabata) sealstone, that unlocks Bisque Doll (Tanabata) when completed.

You can find sealstones for Bisque Doll (Tanabata) in the Tanabata event storyline. You can also fight others for the stones, just like how you fight for Suzuka stones.