Some Japanse laundry starch is based on a mixture of modified rice starch and polyvinyl alcohol (PVA -- not to be confused with polyvinyl acetate which is also called PVA).
It is a critical ingredient in some Japanese bubble juice formulas. It seems to interact in a special way with the Japanese Charmy dishwashing liquid. Mr. Hisao Oono has published his recipe and makes some of the world's most amazing bubble tubes with it.
This ingredient does not seem to have the same synergy with the Proctor & Gamble dishwashing liquids.
Many brands of Japanese laundry starch will work, but you must be sure that they do not contain anti-foaming agents. Some PVA-containing laundry starch contains them, and those brands will not work.
It is not clear if the benefit is from the PVA or the modified rice starch or the combination of the two. Evidence seems to suggest that it is not simply the PVA itself as many bubblers have experimented with adding PVA by itself and found it of limited (if any) benefit.