Is Japanese food hot?

No, it isn't. They don't use a lot of hot pepper and other spices. What they like most in food is freshness, delicacy, and beauty of presentation. They try to use the freshest ingredients available. The preparation should bring out the natural flavors. And the food should look beautiful as well as taste delicious.

Japanese use hot pepper sometimes, but not usually during the cooking itself. They prefer to add it afterwards at the table. They call it shichimi togarashi - actually red pepper combined with some other spices. They only add it to certain things, such as noodle dishes.

And, yes you can get hot food in Japan if you want it. They have good Indian, Korean, Indonesian, Szechuan, and other Asian restaurants in many large cities if they want hot food.