There are three major noodles in Japan. Ramen, udon and soba. All these three noodles are eaten throughout in Japan but ramen probably should be most popular noodle in Japan.
Then, there is a noodle which looks similar to ramen but actually not determined as one of the types of ramen. Tantan-men is a Japanese version of Chinese noodle called Dandanmian, noodle dish originating from Chinese Sichuan cuisine.
Japanese version is served in bigger bowl and soup is milder than the original one. The noodle is topped with pan fried minced meat and vegetables, including bok choy(pak choi). There is also Tantan-men without soup similar to Sichuan's capital Chengdu style. Tantan-men without soup is a local specialty of Hiroshima.
Tantan-men can be found at Chinese restaurants and diners rather than in ramen noodle