Romance manga about a group of legendary children
It really sounds like Yuki wa Jigoku ni Ochiru no ka (Fujiwara Hiro)


  The "military history story concerning boys and girls" revolves around
  Yuki, a girl who has lived in the rural area of Kyoto with her six
  childhood friends who all share a secret that they cannot tell anyone.
  On her 16th birthday, Yuki's fate begins to change.


The story begins with the main girl and boy (the one with dark hair), their friends are not present at the beginning, then the light hair boy comes back and argues with the dark hair boy.

Each child has specific kind of the power, and the girl power...


   comes from Hell