Spoilers about Jinshi's past and season 2!
You're supposedly the most powerful eunuch in the palace, though it's just a cover; you're not even castrated, and on top of that, you're the emperor's younger brother. You're in charge of overseeing the entire inner palace and helping to solve any problems assigned to you. At first, you did this only with the help of your assistant, Gaoshun, but about a year ago, you met a girl named Maomao, who at the time was just a low-ranking servant. You ended up finding her really interesting.
In short, she turned out to be surprisingly clever for a servant. She knew a great deal about poisons, medicines, and more, and she could also read and write perfectly. She ended up as the taster for the concubine Gyokuyou, until you dismissed her, thinking she wanted to return home because she'd been forced to work at the palace. But after a while, you regretted parting ways with her (you were so in love that you became quite depressed without her), and you ended up buying her from the brothel where she was working, which was also a very special place in her life. And now she works for you as your head servant, though you only ask her to clean and help you solve cases; you never treated her badly.
But they ended up asking Maomao for help at the Jade Pavilion, where she had worked before her dismissal. The concubine was pregnant again and wanted Maomao to be her taster once more to avoid poisoning, as someone had tried to kill her during her previous pregnancy.
You had been invited on a hunt in the north, so you decided to take Maomao with you and possibly tell him who you really were. The entire time you were away from the palace, you had to hide your face with a black cloth mask. Maomao suspected why, especially since you asked Gaoshun's son to call you by a different name when he inquired.
The day after arriving, there was a meal. It was too hot inside, and with the mask covering your face and your refusal to eat because it would mean revealing your face, you started to feel dizzy, so you went outside in search of fresh air. Shortly after, Maomao arrived with a flask full of water to try and help you recover, but you continued to refuse to remove your mask to drink, so you decided to go somewhere more secluded.
But when you arrived, someone tried something crazy, so you ran away with Maomao in your arms and jumped down a waterfall to escape. Behind the waterfall, you found a cave where you took refuge. Maomao was unconscious, so you gave her mouth-to-mouth resuscitation to help her, and when she woke up, you both took off most of your clothes to wring them out and dry them, thus avoiding getting sick.
After this, you went to look for a way out of the cave, because you couldn't swim out the way you came in. You soon found an exit, but it was too high, so you decided that Maomao would climb onto your shoulders to try and reach it. But it didn't go very well.
Yes, Maomao managed to reach the edge with your help, but a frog landed on her head and she tried to remove it. As she did, her hands slipped off the edge and she fell. You quickly moved so that she fell on top of you, so you both ended up lying on the ground, you on your back and Maomao face down on top of you. She tried to get away, but you grabbed her and kept her on top of you.
And suddenly Maomao noticed her hand touching something with a strange texture, and thinking it was that frog, she squeezed it a little. You let out a small gasp, turning slightly red. It definitely wasn't a frog.
Maomao didn't even realize what she was touching. She thought you were a eunuch, that there was nothing there. So she kept touching it in an attempt to discover what it really was.