One thing that makes Isogai fanfic in Assassination Classroom special is the exploration of his character. In the original, Isogai is a hard - working and responsible student. Fanfics might expand on his backstory, like his family life. For example, a fanfic could delve into how his family's financial situation affects his dreams and actions at school. Also, fanfics often explore his relationships in more depth. His friendships with other classmates could be developed further, showing different sides of his loyalty and kindness.
Yuma and Tori could be characters from a small - scale, indie story that has a dedicated but not widely - known fan base. The fanfiction allows fans to expand on their relationship, imagining their married life in ways that the original story might not have delved into deeply, perhaps adding more depth to their characters and their connection.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of Assassination Classroom fanfics, and you can easily search for Isogai - centric ones. There are also filters you can use to narrow down your search, such as by rating, length, and genre.
3:10 to Yuma is purely fictional. It was created for entertainment purposes and doesn't draw from real-life events. The plot and characters were made up by the filmmakers.