Denise, thanks for your post. I, too, had recently made the discovery that they list the pasteurization temperature right on the package here. It's very unusual in the US, so I never thought to look. As a few have suggested, the UHT was definitely the culprit.
Since my discovery, I scoured all the supermarkets here in our town and the best I could find is 85 C for 15 min. That is still too high, but does make a better curd than what I have used before. It's good to know that more appropriately pasteurized milk does exist in Japan. We live in a small city and although I would love to have a Coop, the nearest is 90 min away. I know they do home delivery as well, so I may look into that.
I am also going to see if I can track down a local dairy when I get time. I should be able to get an answer on raw milk from the staff there and I will try to post when I do. However, I am assuming that even if it is legal, it may be to much of a bother to them to sell outside their normal channels.
BTW, for the sake of any other cheese makers finding themselves in Japan, I have attached a photo of the milk carton label so you can know where to look for the pasteurization information. Just to note, not all milk lists this information, but most do. The kanji are 殺菌 (sakkin, lit. kill-bacteria) but you can pretty easily pick it out because of the large ℃ next to the number. The time is listed next with 秒間 (byoukan) for seconds or 分間 (funkan) for minutes.