Responses
It depends on who has the copyright and what kind of contract they made with the artist and the writer. Maybe it's financially not worth to continue a project which is already tainted by these kind of allegations.
beta
Is the artist of the mannwa and novel two different people? Usually it's two different people. If so, the artist's wrong deed affect the novelist too then? They were getting profit by selling their story as well. If it's the same person, how could someone who makes stories like this did that?