Breakfast Berry

I had a wonderful authentic breakfast at a Ryokan in Kyoto. However, something had me heading to the bathroom over the course of the morning. Someone advised that the cause was probably a small redish berry that was presented at the start of the breakfast meal. They said it was a kind of natural laxative. Any truth or is my leg being pulled? My wife blames my sake consumption the night before. And the truth is........

I think you ate an umiboshi pickled plum. Was it very sour? X(

First, what you say is about this?
http://en.wikipedia.org/wiki/Umeboshi

If it is indeed umeboshi, then I would say that the alcohol would have a stronger laxative effect than the umeboshi. Ume plums are closely related to apricots, so I would assume that their laxative effect is somewhat equivalent.

From personal experience (I'm somewhat of a self-described umeboshi connoisseur), I regularly eat 5-10 in a sitting without ill effect.

Umeboshi is supposed to cure diaria. The Japanese carry them when traveling overseas. In case the water doesn't suit them, a umeboshi or two will prevent them from going to the potty. But I can't think of any other "red berry" that may be served for a traditional breakfast.

Umeboshi! A plumb? It looked like a small berry. Just one was served. Raw & very sour. I think I ate umeboshi. Definately an acquired taste (like vegemite?) OK - seems it was the sake, or was it the beer.............? Don't tell my wife she was right & thanks for the advice.
DMcV