Custard purin (or pudding, similar to flan) is one of my husband's favorite desserts. We made a point of trying the famed Kobe purin, and it is as tasty as they say. This was the reasoning behind purchasing this particular flavor of Apollo, which a typically lackluster Meiji product.
According to the box, this is a special release for the 40th anniversary of the snack, and vanilla pudding was the number one requested flavor, I'm assuming by popular vote. This explains why the quality of the product seemed better than usual, as described below.
The candies smelled like milk chocolate, and the top portion had a nice, mild vanilla flavor with some caramel notes. The two sections of chocolate blended well, and the cocoa was neither underwhelming nor overpowering. It did taste like purin, and was better than the typical Apollo.
Normally, Apollo chocolate can seem kind of cheap, and it did feel a bit oily at the end, but the flavors were good enough to make up for it. It's certainly not gourmet chocolate, but it had a nice, milky, distinctly Meiji flavor.