It looks like an old sign, way before the Fukushima nuclear accident in 2011. Smaller letters are fading.
Someone snapped the photo, and added the message back to TEPCO in yellow and posted on Facebook, which was then tweeted. (Ah, the age of social media.)
TEPCO: Please do not litter (or literally, please do not throw out garbage). Pristine environment starts with your kind consideration.
Anonymous message in yellow letters: For you to say!
From the tweet by "galeria de muerte":