Piku.jp was the first Groupon style group deal website to enter the market in Japan.
Rain was responsible for the development of the initial system and it's evolution into a major group deal site.
Originally built in Drupal it reach the market, Piku expanded with Japanese mobile and smartphone versions to cover the Japanese market. Later when the site was drawing huge traffic, Piku converted to a fully customised system. Rain were involved in the continual development of the entire service.