I need some suggestions. I am creating an original manga with the main characters being 3 guys and 1 girl. I am designing the girl first and all of them are around the same age (14 for right now). Maybe you could help me with a plot...

-I don't want any of the characters having unrealistic hair color right now.
-It's a realistic setting for now, but I was thinking about giving it some supernatural or odd things regarding the "afterlife" of this story.
-I don't want to make it too old-timey or anything, but modern as in It could happen now.

Sorry I didn't give too much info, but I'd love suggestions so if I ever wanna publish a manga then I can if I have an idea...