This chocolate is called Black Thunder (ブラックサンダー) or Kuroi Raijin (黒い雷神). Raijin is, of course, the god of thunder. Black Thunder consists of chocolate, cocoa-flavoured cookie bits and crisped rice, and it’s been such a success story that a book has been written about its history. (It started small, became popular among university students, really took off when it sponsored the Japanese men’s gymnastics team at the 2008 Olympics and Kōhei Uchimura started endorsing it.) It’s very tasty. Dangerously so.