Pokemon porn comic is neither legal nor ethical. It's a form of content that is considered offensive and against the law. Such material can cause harm and has no place in a civilized society.
This kind of fanfiction could potentially explore Hermione's curiosity or it might be used to develop a complex plot around her character's exploration of different aspects of sexuality. But it really depends on the specific story and the author's imagination.
The first appearance of lesbian porn stories online is difficult to determine precisely. It likely occurred gradually as the internet grew and different types of content became available, without a clear-cut beginning.
There shouldn't be and mustn't be such content. Pokemon is a beloved franchise for all ages, and pornographic comics related to it are completely unacceptable and against all norms of decency.