Your series is Loveless, the tale of a boy named Ritsuka trying to find out the truth behind his older brother's murder. He is entirely alone until a young man named Soubi appears and says he knew his brother, and, whatmore, Ritsuka will now be taking his brother's place as Soubi's fighting partner. This series is overload on the angst, with the question of "who am I?" brought up at every possible opportunity, and Soubi's relationship with Ritsuka is practically servant-master, leading to abuse and thus more angst. Unfinished though the series is, its nonstop creativity is addictive - from the battles to how children have cat ears and tails that they loose when they become an adult (physically, if you know what I mean *wink wink*), there's always something new and unique. This is the series for fans of fun, reflective, philosophizing angst.