ミルク バウム (バウムクーヘン baumukūhen or バームクーヘン bāmukūhen)
Baumkuchen ("tree cake") is one of the most popular pastries in Japan. Oh, how the Japanese love German cakes!
You can sort of make out the "tree" rings, which are the rolled layers of sponge cake.
The label says 東京 バウムクーヘン (Tokyo Baumkuchen).
Found this in the refrigerated section of the Korean grocery store HK Super, next to the castella.