Aether has been travelling the world's with his sister, Lumine, for days now and not once had he seen a red string appear on his finger, but when he gets trapped in Teyvat, he sees the red string appear, and he eventually decided to follow it after a few months of being in Teyvat. At some point, Aether finds himself in Fontaine, the land of water, which is where his string had brought him

So my soulmate is in Fontaine..?