I have a hunch that Sakae met Aoi when in time between his first and second met with Nara. Maybe his golden eyes and hair is because he cant control his influence, just like Hanae's eyes become golden when his influence works. So, my theory is, Sakae is not yet meeting Aoi in his first met with Nara, but then he already meet Aoi and know how to suppress his influence with Aoi's help, that's why his hair and eyes is back to black
I saying this based on Yahiko's copy of Hanae in chapter 67 that Sakae (Yahiko meet Sakae when Sakae already employed by Aoi) had black eyes and hair.
This is also answering maybe the cause he avoided by human because the misfortune they got from Sakae is caused his influence. Maybe his influence affecting people near him. But he can do something about it, you knnow marrying Nara and got 2 children with her without any miserable event.
Edit some typo: Yahiko copy of Sakae. Not Hanae
But he still has golden eyes when yahiko transformed in ch 67 and 68?
Also in the picture from the house demon ch66, sakae has golden eyes?
I think in the early chapters where sakae came back when hanae was just a child, they realized he was aoi cuz of his black eyes?
In ch 58, why did Hanae's hand disappeared when Abeno tried to stop him??
Ch 70, his mom said she met Sakae in High School and the second time they met he had black hair and black eyes,... does that mean it's Aoi-san?
Ch 78, sakae has black hair and black eyes in their family vacation! Is it Aoi or Sakae?