First you must be at least lvl 25 to do this. Go to all of the beast shines and beat all the beast. Then go to junk city. Go to the other side (where you go to exit juck city to go to kyoto.) dont junk city. Go left to a big wall/doorway go though it. Go though that area until you reach any area where you put there beast stone in statues. Beat that area and beat omeaga. Once you do that you get his core. Synisize him and go fight. The best move he has is near death exp. Use it and ta da one hit kills for the rest of ur team.
When you get to the cut-scene about 39% through
the game, in the grand hall, Karin's father is
killed by the Queen of Ice. After the cut-scene
press A near the king's dead body, Karin will say
"watch over me father; I will avenge you!" after
that, you are given the item "God's Ambrosia"
which completely heals own HP and EP. (Very useful
in battle when low on both!)