Yun Kouga

The angels' roles are to assess the progress of humans giving them positive/negative scores based on their everyday actions. The angels, who have deemed that the Earthian are becoming far too destructive, decide that if the Earthian reach 10,000 negative marks, then their world will be destroyed. (Wikipedia)

Twelve-year-old Aoyagi Ritsuka is left with his insane mother as his only family when his brother, Seimei, is killed suddenly. After moving to a new school, he meets Agatsuma Soubi, who claims to have known his brother. Ritsuka eventually discovers that Soubi and Seimei used to be a fighting pair, whereby Soubi was the "Fighter" and Seimei was the "Sacrifice." Now that Seimei is gone, Ritsuka has inherited Soubi, who will become his "Fighter. (myanimelist.net)

One day, Katsumi's girlfriend Sakura suddenly disappears, and all his friends do not remember anything about her. In pursuit of his love, Katsumi finds himself in a parallel world of Japan in the midst of a civil war between two clans Taira and Genji.