On August 15th, 2008, Arai started producing the self-sculpted "Boryoku Genjin" soft vinyl doll, with the name of “NAGNAGNAG.” Thereafter, following “Boryoku Genjin,” he produced other soft vinyl dolls such as “NAGBALL” and “NZOMBIE.” Among his works, many are wearing hand-made costumes and hair.
In November 2008, Arai received an offer from the NY based fashion brand MISHKA, resulting in a collaboration in both art and packaging for “Boryoku Genjin” releases. In December of the same year, Arai started collaborating with COOP, who realized illustrations for packaging and promotional items.
In 2009, Arai produced two short movies in stop-motion about “Boryoku Genjin.”
Since 2010, Arai has participated every year at the New York Comic Con event. Notably, an article about the “NAGBALL” he released in 2013 was published in the New York Times.
Arai has also collaborated with many artists, such as Pushead, Frank Kozik, Tara McPherson, Hi-standard, and Johnny Ryan.