The tapioca will certainly count for a rare ingredient! Mr. Wonder will be excited about getting the starch, and says he'll do some research of what do with it. A few days later, the bakery will be selling batches of casabe among their stock.

Ken will receive full rewards for his donation! Get that bread.

You can determine exactly how this quest went down, and thread (or handwave it) as you please! If you decide to turn in a thread for this quest for gacha points, please reply to this comment with your thread once you have commented at least three times.