It sounds like you may have found a bug somewhere although I think something is being lost in your review through the Google translation. (ちょっと日本ごはできます、でもじょうずじゃありません。)
However, if you post here (even in Japanese) perhaps we can figure out what is going on.
BTW, I think the idea of collapsible TextBubs is a good one, however the multiple child, multiple parent paradigm of Oovium does make the concept a bit problematic. Eventually, however, I hope to develop some way of accomplishing what you're after.