Say the word: Hanabi

Fireworks originated in Asia, specifically, China. They have always been a big part of Asian culture. That's why they are so much more relevant to many artists from that part of the world.

The 形 in 人形 might better be translated as "form", rather than "shape". The word "shape" in English generally coins the image of the silhouette or outside perimeter of an object, which isn't necessarily the case with the Japanese word. "Form" implies the dimensions and general appearance of something.