@CaTastrophy427 yes, u did missed it, Kai already know El as Water Spirit King since way back when they both travelled together for a bit, forgot the exact chapter number
EDIT : So, i found the chapter, Kai found out on chapter 42
@CaTastrophy427 Since he heal the big guy, who almost dying (the one who in love with purple hair girl), the priest is the one who conceal El, saying El is a priest.
How he know? because his dad told the priest to protect his boy
Im just gonna drop this for now, come back in 40 chapters and maybe the dragon will be gone by that part. Holy shit season 2 has been such an absolute slog.