It’s my third year doing snowboarding in Japan, and it becomes much fun after you can balance your body not falling over. Occasionally, even if you fall over, it does not hurt so much anymore.
Japan is one of the best countries for snowboarding lovers, where there is a load of snowboarding resorts, with easy access from Tokyo. The temperature on these moutains usually is not too low so you can enjoy the sport, not worrying too much about the cold weather.