Sorry for the wait, i've been doing research for the rest of this part of the story. Anyway, enjoy.
After going through the portal, Adrien and Marinette find themselves in a white void.
Adrien: Huh... deja vú.
Marinette: How come?
Adrien: Remember Pixelator? This is just like that, except that your with me, not Chloé.
Cooper (echo): Alright, enough talk. Nathan, give them a history lesson.
Nathan (echo): Right...just let me...got it. Let's start with Agreste.
Adrien: What are you...
Jaune (echo): Shhh...you might want to pay attention to this part.
Nathan (echo): Antoine Agreste, born on March, 13, 1850, during the Industrial Revolution. Born into a family of aristocrats in Nanste. He had a rough childhood, as his parents groomed him to become a nobleman, even if they had strict rules. Antoine, however, had different plans. At the age of 15, he would sneak out of his family's estate at every night to see the city for himself. He evetually became part of a gang of teens that accepted him for his smarts and trained him not only defend himself, but also to fit in. He would spend the next 2 years, going out on both day and night to meet up with the "Knights". When his parents found out about his nightly ventures, they forbid him from going off the estate till the age of 20, unless its family matters. With this, Jacque had enough of his strict family. One night, He stole a portion of his families fortune and ranaway to meet up with "Knights" to leave the city. They had an emergency plan...and put it in to action. They boarded a merchant ship that was on it's way to Paris. Once there, they decided to run to split up to find work on their own, while splitting what remained of Antoine's money. On the same day, Antoine found a couple of thugs ganging up on an middle-aged man. Using a cane he grabbed from one of them, Jacque drove them off as the "Knights" came to his aid. The man revealed himself as an agent of the Paris "Order". He offeredAntoine a place among them, to which he accepted. Later, Antoine and the "Knights" took to the streets of Paris to ensure the "Cult" would never get a hold on the city or the country.
Adrien: Wow... is there anything else?
Nathan (echo): That's all you need to know.
Marinette: Now, it's my turn.
Nathan: Okay...just need a second... ah, here we are.
Marinette: Alright, so let's hear it.
Nathan (echo): Jian Cheng, Born on June 7, 1852, during the Qing Dynasty. Her family were servants at the Old Summer Palace, located in what is now the Haidian District of Bejing, China. She was orphaned 8 years later because her parents were killed by Anglo-French forces during the raid on the castle. Jian would spend the next 2 years, living as a homeless orphan, wondering around Bejing for food and work. She would later be drawn to a temple outside the city due hearing it needed a caretaker for the shrine and temple. On her way to the temple, she was attacked by a group of bandits. Fortunatly she found and saved by an old monk who lived at the temple. Upon her first day, she discovered a secret about the place: It was a base for the "Order". When she was caught, Jian was given two choices, either join the "Order" or be left in the woods. Obviously, she choose to join. Jian would then spend the next 5 years training and honing her skills before going on to be one of "Order's" best agents in China.
Adrien: So...what now?
Jaune (echo): Now we begin where you left off.
Adrien: What does that mean?
Cooper (echo): Nathan, give them a summary.
Nathan (echo): Right... in 1877, the Chinese "Order" had defeated the "Cult" and driven them out of Bejing. As the spoils, they secured an artifact: The "Apple". Just as it was being taken back to the temple, the escort was decimated as one of the "Order's" agents, Li Wren, turned traitor and took the artifact. The "Order" received Intel that Li Wren was taking the "Apple" to Europe, specifically, France before moving to the U.S. The Chinese "Order" sent word to their French allies and send Jian to meet up with them and retrieve the "Apple".
Cooper (echo) That is where you begin. You will follow in your ancestor's footsteps as you experience events that they have experienced. You can only watch, you can't interact with them or anyone else. You can't even talk them because they cannot hear you.
Pyrrha (echo): Starting up simulation...sending them now.
Suddenly, Adrien and Marinette begin to disappear.
Marinette: What's happening to us?
Gabriel (echo): Adrien!
Jaune (echo): Relax, their just being prepped for the memory sequence. Your just getting ready to "spectate".
They disappear comepeletly. Then the void begins to change as a 19th century Paris is constructed, along with a morning sky. On the docks, a 19th century steamship has docked. Passengers depart as a hooded figure (wearing white chinese robes with red stitching, stiches soles shoes and black socks, carrying a bag) jumps off the boat and on the dock.
Marinette (echo): Where am i? AND WHERE IS MY BODY?!?
It takes of the hood, revealing a blue-eyed chinese woman with short, black hair .
Marinette: Wait a minute. That woman looks a lot like me. Is that...Jian?
As she walks off the dock, she passes by a green-eyed man with short, blond hair (wearing a derby hat, long black coat, blue vest and white shirt underneath, black gloves, black boots), carrying a smooth, black cane with a small emerald on the top.
Marinette (echo): That man looks like Adrien. Could he be Antoine?
Adrien (echo): Marinette...is that you? I can hear you but i can't see you.
Marinette (echo): Adrien? If i can hear you then that means...
The man then follows the woman off the docks and on the side of the street. He then stops behind her.
Antoine (?): 你好，小姐，你在找人嗎？因為我知道他可能是誰。(Translation: "Bonjour miss, are you looking for someone? Because i know who he maybe.")
The woman then turns around and faces him.
Jiang (?): Seulement si cet homme est assez aimable pour me saluer correctement. (Translation: "Only if the man is kind enough to greet me properly.")
Antoine (?): Ah, you speak French fluently, care to explain?
Jiang (?): Only if you tell me how you where you learned to speak Chinese.
Antoine: I'll explain on the way to my house. I am Antoine Agreste, and you are...
Jiang: Jiang Cheng and shouldn't we go over the details on the mission?
Antoine: Like i said..."on the way"...
A carriage pulls up in front of them. Jacque opens the door as Jiang gets in.
Adrien (echo): So that's them... my ancestor, Jacque...
Marinette (echo): ...and mine, Jiang. But this feels weird. Almost like....
Adrien (echo): ....We'rr living another life. Now i get what Mr. Stérn was saying.
Antoine: (to the driver) Back to the house please.
Marinette (echo): Looks like we'rr stuck with them for now.
Adrien (echo): I wouldn't think that as a problem. Think of it more like a family history lesson.
Antoine gets in the carriage as the driver whips the horse and the carriage begins to pull away.
I hoped you liked it. See how Jiang and Antoine are getting down to business while Marinette and Adrien observe them in Chapter 16: The Stage is Set.