After escaping from the Faceless in the Eternal Stairway, you must conquer Fort Jinya to defeat the Hoshido.
Preparations Before the Battle
Your units will be split up in the southwest and southeast of the map. They won't be able to rejoin each other until you have made some progress northward, so keep this in mind.
Be sure to put royal units on both sides. There are Dragon Veins throughout the map that will knock down specific walls. Select a Dragon Vein to see which wall it will knock down.
Use archers on the east side of the map, as well as units with strong Resistance. There are many mages on the east side of the map. There will also be flying reinforcements on the east side, as well as Subaki, all of whom will fall easily to your archers.
On the west side, use units with high defense to deal with the many club/axe/sword-wielding enemies.
Yukimura is standing on the seize tile in the north part of the map, so you will need to defeat him before you can finish the battle.
You might want to ignore the Dragon Veins in the lower part of the map. Leaving the walls intact means that it will take longer for your units to make their way northward, but the narrow passages will slow the progress of the enemy units and the many reinforcements that show up throughout the battle.
You can begin by keeping most of your units out of any enemy's attack range, but sending one or two of your strongest units to use ranged attacks over the walls to kill the nearest enemies.
Be aware that there are a couple of Mechanists using the Launchers. This will allow them to attack a cluster of your units at long range. If at all possible, keep your units out of the launcher ranges.
Sakura has become a Priestess, so she can now use a bow. However, since she doesn't move, there are only a few tiles that she can attack.
Once your east team reaches the northeast of the map, use the Dragon Vein to break open the wall below the northwest launcher. Then send your west team to the northernmost part of the map. They can use the northwest Dragon Vein to remove the wall east of the northeast launcher. This will allow the east team to use the Dragon Vein near Sakura, breaking open the walls around her. Both of your teams can join up at that point and attack the levee north of Sakura (no Dragon Vein required) and finally break through to Yukimura and attack in pairs. You don't have to kill Sakura, but she will drop a Spirit Dust if you do.