fter the scene, you'll still end up needing to intervene with your allies. You can finish this battle immediately by defeating Xander. If you trained your main character well enough up to this point, this could be the easiest mission you can complete in just a few seconds after starting.
However, if you want to defeat all enemy forces, take note that Xander will not move from his position until you attack him. You can still open the door to the dueling arena by defeating the general on the door and having one of your ninjas to open the door for you. There are no other notable drops in this map aside from the two Sun Festals that will be dropped by two maids.
You can divide your two forces to engage Laslow and Peri's forces. Like always, check your enemy's range so you don't accidentally leave a weaker unit out in the open. Let your sturdier units get the aggro and lure the enemy to your favorable position. Once all other enemies are left and when Xander is alone, he'll start moving and will initiate the attack instead. Finish him off to complete the mission.