Board Thread:Naruto Discussions/@comment-30918569-20200829215844/@comment-32685487-20200901171130

"As a child, Yagura took part in the village's barbaric ritual where Academy students would be forced to kill each other in order to graduate.[2] Following the Three-Tails' revival after being "killed" in Rin Nohara, the tailed beast was sealed within a young Yagura and he learned to control its powers over the following years.[1]"

It wasn't Yagura that was the Mizukage that Zabuza attacked and it wasn't Yagura who had Sanbi when it became free and then was sealed into Rin. Yagura did tell Naruto he was an adult, meaning Yagura was at least 18 when he died.