Ok let me get this straight:
Fon Shen knows Rakan can't afford to redeem her and she will be bought sooner or later. Fon Shen devise her own plan to devalue herself by losing her virginity to Rakan.
Rakan and Fon Shen have sex and Fon Shen gets pregnant with Mao Mao. Rakan doesn't know about this as he is sent to war soon.
Fon Shen who got pregnant, lost her value but decided to raise Mao Mao, since Mao Mao is a love child with Rakan and wants Rakan to see his daughter when he comes back. Fon Shen is happy beause she is devalued and pregnant, she only needs to wait for Rakan to buy her when he comes back.
Rakan has no news of this and has not been in contact for 3 years. During this time, Fon Shen is now depressed that she had been abandoned by him and decided to sell herself to save the brothel which raised her. Due to syphilis, her health worsens and her mind is degrades. She is being taken care of by the brothel since she basically saved the brothel with her body.
Rakan comes back after 3 years and finally sees the letter and her finger, realizing what had transpired. Basically everyone at the brothel blames him for what happened because they thought he ran after making Fon Shen pregnant and skip town to avoid responsibility. The granny/brothel doesn't tell him anything about where Fon Shen is or anything about Mao Mao. Rakan is a broken man.
Rakan happened to see Mao Mao one day and immediately recognize her due to her similarities with Fon Shen. And also saw his uncle who is taking care of her as a foster father.
Rakan then decided to be ambitious and retake his seat as the noble family head in order to make himself worthy to take back Mao Mao. He still doesn't know that Fon Shen is alive and mentally degraded.
Not sure why Mao Mao wouldn't tell Rakan about her mother until now.
Is that about right?
A few holes in this story though. If Rakan knew his uncle is taking care of Mao Mao, then there is no reason why Mao Mao and her step father is living in a hut. Rakan is already an accomplished official at this time. If he really cared for his daughter, you would think that he would at least made sure they would have enough to live comfortably.
The fact that Fon Shen is still alive and not one person in the brothel told Rakan seemed hard to believe. Perhaps it is the last wish of Fon Shen to not want anything to do with him anymore and as respect, everyone held their tongue. But come on, the lower tier or newer ladies or assistant would probably loosen their lips if Rakan would reward them but they probably don't know the history of Fon Shen as well as Mei Mei and Granny.