First off, let me make this clear. In Character Actions have In Character consequences! Do not gripe OOC about your character dying. It happens. A character death will probably be investigated by PC and murder is extremely difficult to cover up or get by. But nor will they 'automagically gank' you. It shall be handled fairly, and by the staff.
If you kill another player character you gain 10% of their XP, -1% for every level they were below you. You also gain one point of reputation for every rank of reputation they had, in the appropriate categories. If you killed an allied shinobi, you lose ranks in devotion equal to the victim's devotion ranks instead of gaining any devotion ranks. Wisdom and Prowess are still gained normally. You also gain 1 CP for every level the victim had.