When you first load
Romance of the Three Kingdoms XIII, it will recommend that you go through Hero Mode to learn how to play the game. Since I have not played any of the previous
Romance games, I cannot tell you if the Main Mode is the same as them. I will echo the recommendation for Hero Mode, as Main has absolutely no instructions on how to play.
When you start up Hero Mode, you will see only one scenario that you can play. You have to unlock the scenarios in Hero Mode in order, but you can go back and replay a previous one at any time. The first scenario starts you with Liu Bei, who starts out the son of a weaver. This is further back than I remember the other games explaining. He signs up to fight against the Yellow Turban Rebellion as he is idealistic and worried about the chaos the rebellion will cause. He first meets Zhang Fei when he is looking at the sign-up poster. Zhang Fei introduces Liu Bei to Guan Yu. Long story short, they both follow Lui Bei since he wants to restore the Han Dynasty for the people. The next scenario takes you over to Cao Cao, who has to leave town and gather people on the road after failing to assassinate Dong Zhuo. After that, you go on to Lu Bu, who also has his hands full with Dong Zhuo. While you are getting the history lesson, you are also learning how to play the game from the characters that best represent that part. Liu Bei teaches you about visiting people and making contacts, while Cao Cao teaches you how to force your rule and debate and Lu Bu teaches you about fighting. As you keep on going, you will learn more and more about how to gather people and rule an entire nation.
Once you have learned these lessons (or maybe before you complete all of them, if you are impatient), check out the Main Mode. Here, you will select a historical scenario and see if you can manage to complete it. You do not have to go in order and you can select any of the scenarios. After you select a scenario, you can then select an officer to start up the scenario. You can view the recommended officers and historical officers. You can select any of them, but your choice will determine the difficulty of your game. After your officer selection, you can change out any game settings that you want.