Is or a shounen or a seinen. Is about a woman that is a very, very good fighter and female bodyguard. She saves a boy from falling in a river or something, and he turns out to be the prince. His mother asks her to protect him, cuz he has this evil water sprit inside of him and there are a ton of ppl trying to kill the kid.

Can somebody pleease help me? Thank you so much in advance.

Is it Seirei no Moribito?

Yess, thank you so much