Rights violation of a joint-work
If the clay object has artistic elements and thoughts, Right-kun is violating article 117 of the copyright act.
Joint work is work that has been made by more than two people in cooperation, and the rights concerning the work may not be used individually.
the rights, in this situation, is to do things that are considered violating the rights of the authors without any approval from the co-workers of the work.
(Preservation of rights to anonymous and pseudonymous works)
Article 118 (1) The publisher of an anonymous or pseudonymous work may file the claim referred to in Article 112, Article 115, or Article 116, paragraph (1) or may claim damages or the return of the benefit of any unjust enrichment in that person's own name, on behalf of the author or the owner of the copyright to the work; provided, however, that this does not apply if the pseudonym is the name by which the author is commonly known or if the true name of the author has been registered as referred to in Article 75, paragraph (1).
(2) A person whose true name or the pseudonym by which the person is commonly known is indicated in the customary manner on copies of an anonymous or pseudonymous work as the name of the publisher of the work, is presumed to be the publisher of that work.