Number (manga)

it's something like another version of black cat...the story lah~, i think...?
it's about assassination... this boy, the main character wants to get revenge on someone who killed his parents long ago so he joins the same group as him but that guy is the top rank while he is the fifth, so there's a big difference (to him lah~) So now this story is about his current life of an assassin... And how to get revenge on that person while dreaming to get to the Yggdrasil, the World Tree... (Their base is called Asgard, named after the home of the Norse Gods) lol~