This is so funny to read, because where I work (Disney), the Japanese guests are our loudest and most enthusiastic. They definitely smile the most and take the most pictures, and they're always so excited, I s'pose because in Japan they are not allowed to actually touch the characters, where they can here. The last thing I thought them to be culturally was quiet and reserved!
One thing that might be noted - many Asian cultures (Japenese included) are very big on gift-giving. Very, very big. As a courtesy thing.