As a fan of web novels, I wouldn't recommend any particular doujin novel because it depends on personal preference and inspiration. However, I can provide you with some advice on the Sword and Sword Arts Realm and Naruto Doujin novels. If you want to write Naruto Doujinshi, you can consider creating a new character because it allows you to explore the Naruto world and the inner world of the character more deeply. Of course, you can also try to write a story about Dai Tu as your main character because he is a very popular Naruto character with a complicated character and rich story background. If you want to write a Doujin novel in the Sword God Realm, you can consider setting the story in a different world or timeline so that you can explore the different elements and characters in this world. In addition, you can try to create a new character, such as an alien from the Sword God Realm or a character with special abilities. This will add freshness and variety to the story. Regardless of whether he chose to write Sword God Domain or Naruto, the most important thing was to maintain the uniqueness and creativity of the story and strive to make the characters and plot attractive and readable. Good luck!