Responses
Hmm, I don't think so. The novel ends right before they start college (leaving open the possibility of a future story about them as adults), so I don't think we'll have any 18+ extras here unless the original ending is modified a bit...
This will probably follow the same route as Summertime where the actual smut happens in the side stories, though I'm not sure if this is going to even have side stories. I don't think anything is confirmed yet.
If you just want to know how the artist (Jinwol) draws smut though, you can check out "No Sex Zone," it's not uploaded yet but they are part of the anthology and their title is "Beyond the Safety Line"