Feral Corpse
I'm sure if I say 'Hey, Name 18 characters from Final Fantasy' or 'name all the characters from Lord of the Rings, Simpsons, or Family Guy', they'd do it real easy like and then look at you like you're stupid. No offense to the rest of you, but you're not thinking from a fresh perspective. Some of you are just being harsh and all over the place.
How many of these characters end up pretty useless in most anime? A hell of a lot in shonen. Lord of the Rings has a lot of characters too. Guess how many got cut in the movie because they added nothing to the story? Many added to the overall world, because that was where Tolkien's interests lay.
And also: these guys are pros. A lot of them worked up to this(and a lot of TV shows have multiple writers). You learn crawl before you walk, and you learn to walk before you run.
Our usual advice is to do a 5-30 page comic before a sprawling epic. Most don't listen. I painted myself into a corner with too many main characters in an epic when I was younger, and they were still nowhere near 18 mains.
There is value in starting small in many instances.