Tsubasa Reservoir Chronicles and Tsubasa Tokyo Revelations.
Basically, chronicles is about a clone named
Syaoran (who doesn't know he's a clone) who falls in love with a princess named
Sakura (oh the cliche!). By some act of god, she loses her memories (which turn into feathers) and he has to get them back. He trades his most precious possession (his relationship with the girl) to a witch who then gives him the power to travel to other universes and find her memories. The thing that sux is that all the memories erase him completely and the girl will never remember that she liked him too. Towards the end, the real Syaoran (who is actually called
Shaoran) appears when the clone begins to lose his artificial heart/soul/humanity. This occurs in Tokyo Revelations. They follow each other and eventually have a standoff with Sakura suspended in a floating bubble. The two have an epic battle, but Sakura and her godly powers break free and she tries to stop the fight. She gets killed by both guys at the same time. Tears fall everywhere.

Almost as hard as fighting a Holy Paladin.