Here's an abbreviated explanation from the original blog post:
FUCKIN' SALE. In flashy Osaka, the use of English for decorative purposes in Japanese advertising reaches a new peak of perfection.
There are some stories that explain themselves pretty f*ckin’ eloquently.
God knows what the people in this Department Store in Osaka were thinking when they came up with this advertising slogan but Zarina Yamaguchi, a friend of a friend, was thinking "pretty damn funny" when she snapped this picture on January 4th. Zarina explains:
Well, a childhood friend of mine and I were strolling along the local street in Shinsaibashi, Osaka. [...] I walked into this store to check some things. Truth is, I didn’t even notice the posters. When I looked around, each corner had posters that printed 'fucking sale'. I didn’t know how to react but what caught me by surprise was that none of the people around me seem to understand the profanity. My friend Sarah and I, both of mixed Japanese descent, both bilingual in Japanese and English, were struck with the comical twist. Pretty sure I would have never seen this elsewhere, I had to snap a shot.