|After clearing this battle, you will be on the Historical route for Jin's story. For the beginning of the Hypothetical route, go to 8W - Battle of Xuchang.|
Go east until you find some officers, so defeat them and then head north to the objective. Some rebels will ambush you, so defeat the three unit commanders (as well as the officer just for fun) to clear it. It doesn't seem Sima Shi is here, so go north into the next area.
As soon as you step into the next area, you'll see some peasants asking for help. There is one on each of the paths in the vicinity and all you have to do is defeat the Unit Commander fighting each peasant. After rescuing all three, go north through the now opened gate and search the three spots for Sima Shi. While exploring these three spots, the gates to the area to the west will open.
You will notice that Sima Shi's bodyguards are in the area, but they are surrounded by rebel forces. As you did earlier, defeat the three unit commanders to rescue the bodyguards, who tell you that Sima Shi is in the garden area to the north. Before you even get the chance to rescue him, Sima Shi is defeated.
Defeat the rebel forces in the area, which will trigger Wen Qin's appearance in the eastern side of the map. All that is left is to go over there and defeat him to finish the battle.