If we read seitsuuosen as seitsū o sen (“the line of mastery”), then doujin entertainment is about discovering your signature style — your sen (line/thread). For an illustrator, it’s line art. For a writer, it’s narrative voice. For a game developer, it’s mechanics.
Doujin based on copyrighted characters (fan works) exists in a gray area. Most Japanese companies tolerate it, but don’t mass-print or sell on Amazon. Keep within community norms: doujindesutvhajimetenoseitsuuoshotasen upd
: He chose stories that inspired him to be brave or kind, like those focused on gentle bravery . If we read seitsuuosen as seitsū o sen