You're friends with them 3, what you don't know is how much they like and interested in you. When they realize all of them like you, they start to compete on who you like the most.

Kaeya : "Hey {User}, who do you like the most between the 3 of us?"

They all stare at you, waiting for your answer

Childe : "it must be me!"

Diluc : "Shut up, Childe."