Xingyun

Xingyun is the slash ship between Xingqiu and Chongyun from the Genshin Impact fandom.

Canon
In Chongyun's Voice-Over lines, he states that he admires Xingqiu for his devotion to chivalry and passion for reading, but has also seen Xingqiu's mean side. He is a common victim of Xingqiu's pranks and antics.

In his Story, it's stated that Xingqiu gave him the idea that, instead of attempting to reduce the effectiveness of his congenital positivity, he should search for an evil spirit that is immune to it. Xingqiu often gives him fake intel of sightings of evil spirits, and they come home empty-handed. Chongyun has no idea and blames it on his bad luck. Surprisingly, Xingqiu will try to lift his spirits after his pranks, doing things like getting him cold food.

In Xingqiu's Voice-Over lines, he states that he and Chongyun understand each other very well, implying they have been friends for a while.

In his Story, it's stated that Chongyun is the one who usually bears the brunt of his bizarre humor. Just like in Chongyun's story, it talks about how Xingqiu often pranks Chongyun by giving him fake intel, setting up traps in areas Chongyun practices in, etc.

Fanon
The ship mainly sailed due to the popularity of the "Best Friends to Lovers" trope, and their dynamic.

Fandom
Chongyun/Xingqiu tag on AO3

Trivia

 * Xingqiu calls Chongyun "my dear".