Asked a friend. Says he that the writings are about "Thank you for purchasing the product". There are also Ushio's name and both devil and sex/gender are mentioned.
魔性の潮 is "Devilishly Attractive Ushio":pools/9300 which is the name of one of the pools Himura made. Presumably, this was at the back of a book, or otherwise posted in response to that book being sold.
... It just happens to also imply that Ushio, herself, is being sold.
