Note: Updated below the dotted line on, January 12, to add the answer.
One of my students is married to a doctor and he often receives gifts from his patients. Sometimes, she passes these gifts on to me because her husband tends to receive far more than can be consumed by her family, and she's a nice person and wants to give me nice things despite suffering some financial hardships as of late.
Most recently, she gave me the bag you see pictured on the right in the photo above. I had no idea what it was and if I had to guess just by looking at it, I'm not sure I would have been able to discern the nature of its contents. The plate on the left is one of the items after being placed in the toaster oven for a few minutes which is something she recommended I do.
I thought I'd give my readers a shot at guessing at what this is by making comments with their guesses. I'll update this post with the answer some time within the next 24 hours. Happy guessing, friends.
(Please note that any comments posted through the night Tokyo time won't be moderated for about 8 hours so there will be a delay in posting them, but they will be posted in the order they are received!)
Those living in Japan who took a guess had a distinct advantage over those who live abroad since they may have encountered this item before. That being said, though I live in Japan (as does my husband), I hadn't seen this delicacy before. My husband guessed it was some sort of dried beef and remarked that "it looks even worse in person" (than in the picture). I thought it was flayed eel.
The picture is of dried sweet potato. Despite how bad it looks, it actually pretty much tastes just like a sweet potato, though the texture is somewhat different.