Nikuman (肉まん; derived from 肉饅頭 niku (meat) manjū) is a Japanese food made from flour dough, and filled with cooked ground pork or other ingredients. It is a kind of chūka man (中華まん lit. Chinese-style steamed bun) similar to the Chinese baozi (包子), Also known in English as pork buns.
Nikuman are steamed and often sold as street food. From about August or September, through the winter months until roughly the beginning of April, Chūka man are available at convenience stores, where they are kept hot. -(Wikepedia)