If you adapted a Japanese drama to write a novel and did not respect the copyright of the original work, it might constitute an copyright violation. Any adaptation, translation, creation, or exploitation of another person's work under copyright law must be permitted by the copyright owner. If you don't get the authorization to make an adaptation, it may constitute copyright violation. When adapting a Japanese drama to create a novel, you must respect the copyright of the original work and not violate the intellectual property rights of the original work. Otherwise, they might face copyright disputes and legal proceedings. In order to avoid the risk of copyright violation, it is recommended to first understand the copyright of the original work and obtain the permission of the copyright owner before creating. At the same time, they could also consider seeking professional copyright lawyers to help ensure that the adaptation was legal and compliant.