Dialogue and interaction between characters are what can make people care about them. But not just any interaction will do. Make it meaningful, and interesting. Have the reader learn about the character, by the way the character interacts with the world around them.
This brings up another point, don't neglect the supporting cast. They are just as important as the main cast, helping to embellish and flesh out the story just as much. Often, the supporting cast are the plot generators, introducing problems, puzzles, and abilities to the main cast, among many more things.
Work on villains too, and establish them in the story. Who are they, why are they enemies with the main cast, what are their motivations, how important are the motivations to the story, what can they do as villains? That sort of thing. Hero is only as good as their villain, that's why Batman and the Joker are so fondly remembered by readers. Same with the X-men and Magneto, or Spiderman and Venom. Make the readers enjoy the villain as much as the heros, and make the villian believeable in what they are doing, why they are doing it, and such.
Thanks for the advice, I will make sure to make the supporting cast just as important as the main character. My sister and I are having trouble coming up with good villains but your advice was very helpful thanks!
Unfortunately, your plot is painfully cliche. Read some books, generate new ideas, broaden your horizons! Try something new and break out of your comfort zone.
Or, if you're really set on this plot, you're going to have to work hard to make us care about the characters and the story. Sharpen those writing skills! The concept is typical, but the actual story and what goes into it doesn't have to be! A lot of the time, it's not the story that's bad, it's how it's been written. So it IS possible to have a cliche summary, but it COULD still be a fun read. If you write it well.
I definitely encourage you to broaden your horizons, though. Nothing nurtures creativity like a vast pool of inspirations.
And make sure there's a point to your characters. Don't just write them because you want a host of cool characters to draw in pretty pinups for your story. They need a point, a reason to be there, otherwise they're painfully transparent, two dimensional toys for the fans to play with.
Manga is art AND writing. But the true art is getting them to work TOGETHER. You need to be just as good at writing as you are at art. It's so important to remember this.