The Japanese word for pumpkin is kabocha (traditional Japanese) and pumpkin seed is kabochanotane.
Interesting facts about pumpkins in Japan
The Japanese have been growing pumpkins shortly after 1542 when Portuguese traders first brought them over. Today there are two varieties of them being grown in Japan – the regular Western pumpkin which is the most common one you will find and a unique black colored Japanese variety known as kabocha.
Kabocha is a black skinned winter squash cultivated by 10 different growers in the Miyazaki Prefecture of southern Japan. What makes kabocha so popular in Japan is that they are much sweeter than regular pumpkins, are easy to cook with and they contain far higher nutritional values too.
Read more about them here.