Maybe because he died as a 14 yo. so he cannot develop further then a 14yo. child?
Just because you’re 14, it doesn’t mean that you stop developing. Yukine is mentally growing to fight and protect people and he would rather risk that in order to find the truth. He risks Yato’s existence cooperating with the biggest enemy. Why would you wanna ever cooperate with someone who intends to continue hurting people you care about? And to risk it for some truth that shouldn’t mean anything after death?
It was stated earlier that they will remain children, pretending to be adults.
IMO Its kind of the point that they are trying to portray here. No matter what experience a human has, they will still continue to seek what they don’t know and what they don’t have (human’s nature of being greedy) 14 years old or not, greed affects anyone... plus “father” also made that corruption faster through making him think how Nora died.
Yukine: yAtO hiDeS ThIngS fRom mE.
I’m so disappointed in Yukine. There are obviously reasons why Yato is keeping it a secret. Safety reasons. It’s as if Yukine is selfish enough not to care about his friends like Hiyori. It’s like he lost all of his character development from the first arc. Yato literally said, “I gave you a human name, so live like one.” And Hiyori was happy to tutor him like a school student so he can grow. So why is he going back to being the plain selfish coward risking your life to seek the truth when you are given the chance to start over again?