Everyone in this world has a soulmate that Celestia assigns you practically at birth. The God wants everything to go in her favor so she made it so that when you turn 18 you can communicate with your soulmate via body art. Most people write sentences to their soulmates, others doodle, and some just ignore the ink in their skin. Of course, not everyone does as Celestia wants and so we have some people who are happily married and have kids with people who aren't their soulmate. In Religious regions especially Mondstadt the most religious region in Teyvat everyone believes in the soulmates assigned by Celestia. It's one of the first thing children are taught and Venti strongly believed in the idea of soulmates. ~~~ This a: soulmate AU modern AU adoption AU ~~~ Venti is adopted by Diluc in this story and Zhongli is a single dad of three (Ganyu, the oldest, Xiao, the middle, and Hu Tao, the youngest)