Nakatsuji also admitted to have used copyrighted images of popular anime characters to spread it via the Internet.
The malware, which earned the name Harada in the Japanese media, was distributed via the P2P file-sharing network Winny. The Trojan was designed to delete music and movie files, while presenting the user with images of popular anime characters.
Ironic enough, Nakatsuji was not charged with anything related to the malware itself, but with copyright infringement and defaming an acquaintance by embedding his photograph into the malicious code.
A similar decision was taken in the case of Isamu Kaneko, the author of the Winny file-sharing program. Kaneko was fined in December 2006 for assisting in copyright violation.
Nakatsuji was arrested back in January, along with two other men who helped Nakatsuji to distribute the malware.