In this map, you have to rout all the enemies. Saizo, Orochi, and Reina are located SE of your position. They’ll be moving independently and will attack enemies within their range. You have to bring your avatar there and talk to Saizo only to recruit them to your party. There’s a lone chest to the NE, behind a gate near the map’s boss, Kotaro is located. The area is hard to navigate for foot soldiers because of the thick woods terrain. Fliers will be an excellent choice to move your units; just be careful of enemy archers.
There are hidden spike traps in some of the terrains which will damage all units in the terrain at the end of the turn. You can disable these spikes by activating the nearby dragon vein. Almost all of the enemies here are ranged so make sure that the enemy range is displayed on your screen before positioning your units. Making contact with Saizo will be your top priority. After talking to him, you'll be able to recruit him, Orochi, and Reina to your army, making it easier to rout the remaining enemies.
Remove the spike trap terrains only after dealing with any nearby enemies. Once done, make your way to the NE to confront Kotaro and to loot the chest containing a Master Seal. You’ll also get a Steel Shuriken from Kotaro after defeating him. At the end of the chapter, Kagero will be joining your team as well.