In Gintoki x Shinpachi fanfiction, their relationship is often one of deep friendship. Gintoki is like a mentor figure to Shinpachi. He guides Shinpachi through the chaotic world they live in. Shinpachi, on the other hand, respects Gintoki a great deal and is always there to support him. They have many comical and also heart - warming interactions that make their relationship a central and interesting aspect of the fanfiction.
Another characteristic is the exploration of their growth. Both characters have room to develop, and fanfics often take advantage of this. They might grow in terms of their skills, their understanding of the world, or their relationship with each other. For instance, Shinpachi might become more confident under Gintoki's influence, and Gintoki might become more responsible in Shinpachi's presence.
One common theme is loyalty. Gintoki and Shinpachi are always loyal to each other in fanfiction. Another theme could be growth. They both grow as characters through their interactions. Also, the theme of family might be present, as they act like a family in some stories, with Gintoki being the more experienced 'older brother' figure and Shinpachi the younger one who looks up to him.
I recommend the book "Possibly a Fake Silver Soul". It tells the story of Jiang Cheng, a transmigrator, who met the owner of Xinghai District and his girlfriend, Jiang Hua, who were traveling in the universe in the dragon vein of a certain planet. Later, he came to Earth and met his teacher, Yoshida Shoyo, who had influenced his life. He also met a group of friends. This included the transmigrator Okita Soki. This is a Silver Soul Doujinshi novel, don't miss it. I hope you like this fairy's recommendation. Muah ~😗
Gintama is purely fictional. It's filled with imaginative characters and scenarios that are not rooted in real-life events. The creators crafted a unique and entertaining fictional world for the audience.