How to Get Married
You need to enter Taoist temple in one of the cities (it’s big temple inside the city) during the day with max relation marriable character being in the party.
Then the scene with bickering woman and her husband triggers. During this scene you learn about existance of the temple on another location. Go there.
Have a scene. Kick out everyone but your future waifu from a party, save the game and reenter location.
You either will be asked straight up to sacrifice marriage stone, or will be required to answer the question first.
I hope this helps. Have a great adventure!