You need to fulfill all the other conditions first. All stars on all stages up to Chibi, then when you do Chibi from the camp you need to talk to the guy with the Golden Arrow above his head to start the Hypothetical stage. Follow all the missions and complete the stage after that and it will give you the star on Chibi and you will open the bottom path.
Mans greatest weakness is his own mortality. How quickly we forget that 100yrs is a very, very small amount of time
I've done all the special conditions for all levels up to chibi. But the special condition for chibi....idk what it is. Is it me just having to start the alternate storyline?
If I remember correctly, if you start the map and see Guo Jia next to Cao Pi, you're ready to start the hypothetical timeline. Guo Jia should have a yellow arrow on top of his head and Cao Pi should have a purple one. Talking to either one should give you a warning prompt as well telling you what path you're going down.
If you just see Guo Jia standing to the side looking over the water's edge, then you've missed a condition in a previous map that you need to fulfill in order to trigger the hypothetical.
As for the special condition for Chibi - just play the map normally through the hypothetical route. It should reward the star for it.