personally, I think for moshang baby trapping I don't even think they had sex for the baby trapping. I think mbj just walked in and said he was pregnant and told sqh the kid was his and sqh filled in the blanks with wifeplot and weird mpreg artifacts and did not think twice on it because he's sleep deprived and at this point just rolls with this shit. We're already in this deep. Sure we stood in front of the magic mpreg mirror and ate some fruit or something and now I'm a father on top of overworked; just throw more synonyms for exhaustion at me and we'll add them in. What's more.
There's already a baby in there might as well get hot sex before i die. Really though Mobei-Jun needs like one more ingredient in his mpreg plot contrivance and it's Shang Qinghua to confess his love and manages to get that before the end of his first trimester through hard work and emotional honesty and becomes magic pregnant. So Mobei-Jun completes his ass backwards plan so he can ride that dick hard enough to get a perfect A+ in pregnancy and banks on the fact that Shang Qinghua doesn't know enough about this to notice the timeline is off
Bonus content for what I think happened in this cannon scenario *ahem*
1. Mobei-Jun never tells Qinghua about the obvious baby trap fuckery being a lie and Shang Qinghua will not put this together until it's pointed out to him by a eye rolling Cucumber Bro who's just like: dude how are you stupid like this?
2. Shang Qinghua insists on bottoming first before Mobei-Jun gets to have his dickie wickies. Because man is convinced there's no way that Mobei-Jun a man so seme coded would ever want to take his dick. Its a bad time mostly because size shit is too much and it's then Airplane realizes his ideal man is too big to top but like... Dat ass. And sheepishly offers that next time maybe he can top just a little.
3. Mobei-Jun plays it cool the entire time thats being offered but he's screaming YESSSSS in his head. The fireworks and champagne bottles are popping.
4. The 'magic mpreg mirror' they stood un front of that time was not real. Mobei-Jun hadn't found it yet and it won't work without a love confession anyway. He commissioned a fake before finding the real one the next week and again Qinghua didn't notice.
5. The other advisors are begging the king get an abortion or at least properly married and Shang Qinghua is like yeah I can arrange you with like a good political match so Mobei-Jun says 'you plan to not be in our child's life? Is that it?' And Qinghua panics and swings the other way and says we will be married in the morning if we have to and they are
5. Mobei-Jun insist on wearing the bride robes but Shang Qinghua is like wouldn't that be inappropriate? And Mobei-Jun wears the bridal dress and insists on being kissed right before the wedding.
6. The way Mobei-Jun got around the timing issue is the mpreg baby spawns in like 8+ weeks pre-made so basically Qinghua woke up and was like huh... my king is rounder than I remember but and went back to bed.
