The enemy has five groups on the field: Roeas, Castanea and three squads. You have an additional guest union, fighters from Celapaleis, but don't expect much from them beside from being another target (although their healing capabilities are useful sometimes). The enemy is reinforced by two additional squads in the first and second turn.
|Spoiler warning: Battle tactics.|
Head for the enemies at the right side first and finish them off, the ones on the bottom won't engage you until you get close.
Roeas and Castanea will stay on standby but the accompanying unions will go for the fighters from Celapaleis. Head for them after finishing the enemies on the right side, this should give you another turn without the bosses. The Magus squad is the most dangerous so try to take it out at first.
The biggest danger is the Overdrive skill Roeas or Castanea will use when the other one is defeated. It gives them four attacks per turn. Roeas is the easier enemy in this state so it's recommended to defeat Castanea first.
The fight yields 14,675g.