Needs 2 go in2 opFound this guide/walkthrough for book 3 and 4 on reddit:
You must be registered to see the linksYou must be registered to see the links(Link to the book 4 love rote which has the link for the rest of the books)
Credits to "triharderr"
This is a guide for Book 3 (love/slave) and 4 (love/slave) but it seems book 4 is not complete.
Its good enough if you use the mod from lain that covers book 1/2 and this one to finish the last 2 books.