We have three endings
Good Ending
Bad Ending
Normal ending
Requirements:
Good Ending: Save Serra, Save Sige, Defeat Genesis
Normal Ending: Kill Serra, Injure Sige
Bad ending: Kill Serra, Kill Sige, Kill Genesis
What happens:
Good ending: Genesis has been defeated, the powers in humans have started to dull and technology is coming back into use. The school year is completed and all the students that were possessed have recovered. All the Shades have retreated to Dusk and remain trapped there.
Normal End: Sige has been defeated. The school year is completed and all the students that were possessed have recovered, and the Shades have gone been banished back to Dusk.
Bad Ending: Serra and Sige have been killed. The possessed students have died, the world is in chaos. MC has lost the last shred of humanity inside his tattered soul and must be stopped. You have no choice but to take his life.
STORY SPLIT:
If you manage to kill MC: MC's tired and tortured soul is finally put to rest, and his bloodlust staved. The world goes into a shaky peace, with the memory of thousands of dead students still haunting them.
If you are defeated by MC: The onslaught by the troubled soul continues over the face of the earth, with no one able to stop his power. Soon none will remain of the world.
NOTE: You don't get to continue once you are defeated by MC.