A 'cc0 visual novel' is a visual novel that comes with a very special license - CC0. The CC0 license is a powerful tool in the creative world. For visual novels, this means that the developers are giving up their rights to the work. It could be for various reasons. Maybe they want to contribute to the community in a big way, or they believe that their work could be improved and expanded upon by others. As a result, anyone can take the elements of this visual novel - be it the plot, the characters, or the overall design - and use them in their own projects. This can lead to a lot of new and exciting derivative works based on the original CC0 visual novel.
Adding CC to a story isn't too complicated. You could start by writing out what you want the captions to say. After that, find a platform or app that supports caption addition. Make sure to sync the captions with the relevant parts of the story for a seamless experience.
It's hard to give an exact time as it depends on the manga's plot development. But typically, Yuta Okkotsu shows up when certain events and character arcs lead to his introduction.
Corporate CC fan fiction is a form of fan - made fictional stories related to a corporate - themed or corporate - branded 'CC' (which could be a company, a corporate character or something specific within a corporate context). It often takes elements from the corporate world and weaves them into fictional narratives, usually created by fans who are inspired by the corporate entity in question.