How do あなた come up with your characters?

Well.... my soul 'absorbs inspiration' from a variety of areas and experiences, before filtering out the ones which seem the awesomest, then I use those as a base for my protagonists. I solidify their 全体, 全体的です appearances and personalities によって giving them my own traits and qualities, so that I can connect with them better and basically express myself through them. However, I give them certain things which sets them apart from me uniquely.

To sum it up, the protagonists are different versions of my own self, just with some qualities which I'd like to have - but currently don't (e.g I'll give them blue eyes, because my eyes are brown and I think they're boring.... または I'll give them magical powers, which I obviously don't have!).

The protagonists' enemies, friends, those other people.... they're then conjured up によって my mind, mostly based on my own enemies, my own loved ones, etc.

I hope I made sense!

I don't really come up with them: they come to me.

Usually, if あなた have a story idea, your main characters just come with them. They typically balance each other out automatically.
If あなた need a minor character though, think about the role あなた need that character to play in the story and go from there. Decide their personality, and base their appearance off of that. If あなた can't think of a role though, あなた probably don't really need that character.

I come up with the plot first and then I come up with the characters cause whatever my plot is that's how I decide what I want my characters to be and what they'll do and bring to the story. I hope that makes sense :)