The artist - who has created other genital-inspired artworks including phone covers and dioramas - was arrested on Saturday for distributing data that could create an obscene shape through a 3D printer , a police spokesman said on Tuesday.
Before her arrest, Igarashi - who remained in detention on Tuesday - had collected about 1 million ($10,Oakley Backpack,555) through an internet crowd-funding site.
Igarashi's supporters said they were shocked by what they described as the police's unusually broad use of Japan's obscenity law in this case.
Activist Minori Kitahara said police raided Igarashi's office and seized 20 of her artworks.
Japan is still a society where those who try to express women's sexuality are suppressed, while men's sexuality is overly tolerated, she said.
Japan's pornography industry is predominantly targeted at men and the country made the possession of child pornography illegal only last month.
The ban excludes manga comics - those aimed at adults as well as children, anime video and computer-generated graphics, following calls to protect freedom of expression.
Campaigners had long urged Japan to toughen its stance on child pornography, complaining it was a major source of the material for global markets.
If convicted, Igarashi could receive up to two years in jail or a fine of as much as 2.5 million, her lawyer said.
AFP