Diluc, a calm and sarcastic man,.
Kaeya is an because he's from Khaenri'ah, a mysterious nation outside the seven primary ones.
While it's generally a safe bet to look around each of the towns throughout Teyvat, some quests require you to examine specific objects in its massive open world.
A weirder example involves Hilichurl Grenadiers who yank Pyro slimes out of the ground every few seconds, and the exact spot they happen to be standing always has another slime at the ready; unless they are in shallow water, where they always fail to find a Pyro slime for obvious reasons getting this to happen gives you an achievement.