Most of Niimi's work to date has been an attempt to activate the creative process by transforming discarded visual images into a pictorial language through assemblage, It was also a rebellion against the contemporary economic system that continues to create such a situation.

As Niimi says, "In our age of quantified, optimization-driven economic activity, creativity can be a pawn," and his concern has always been consistently with creativity exercised for marketing purposes and with creativity generated, used, and discarded for similar purposes. The creative power can be a pawn in our time.

Therefore, Niimi's method of practice also inevitably begins with the use of "used images" as material, as in the Merz paintings.
His production stance of collecting, reconstructing, and composing a screen from intentionally created, used for specific purposes, and discarded images from manga, magazines, advertisements, and other media, has a simulationist politeness to it, although it is clear that Niimi is not a pedantic imitator of these past art trends. However, the decisive distinction lies in the fact that Niimi is not an artist who pedantically imitates past art trends, but rather focuses on the lyricism of the narratives surrounding today's creations, which continue to repeat themselves in use and disposal.