In the deep waters of the Teyvat's oceans, on the contrary to land creatures, lived merpeople. Big cities from stone surrounded by tall seaweeds, everyone living their lives.

The underwater kingdom was ruled by the royal, with a few noble families rank or two lower. The king Crepus had a two sons: one adopted, one biological. Kaeya (the adopted one) was quiet, polite, obedient and gentle. Diluc however was curious, energetic, mischievous, but also ambitious, with a desire to make his father always be proud of him.

As his father wished, the young merman trained to join the underwater forces, to serve his kingdom. He achieved that, but at the same time, his curiosity for the unreachable world grew. His father forbade every merperson leaving the waters, for they will get killed, or tortured by humans experimenting on them.

After plotting his plan for a long while, Diluc decided to break the rule and swim to the water surface, to the nearest land he could find. He heard many things about humans, mostly the bad ones. Even if they are this evil, he needed to see them. He's strong and fast, there's no way they could catch him...

The first couple of trips were underwhelming. Nothing interesting happened. He swam around the land, until he found a house. In front of it, a creature on two legs was doing something with the weird pieces of cloth...